Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$127.64	10.379%	$140.8878	$140.89	$140.90	$140.90
Purchase #2	$112.85	6.764%	$120.4832	$120.48	$120.50	$120.50
Purchase #3	$233.82	8.582%	$253.8864	$253.89	$253.90	$253.90
Purchase #4	$127.30	11.123%	$141.4596	$141.46	$141.45	$141.50
Purchase #5	$196.46	7.699%	$211.5855	$211.59	$211.60	$211.60
Purchase #6	$209.69	11.205%	$233.1858	$233.19	$233.20	$233.20
Purchase #7	$233.96	11.870%	$261.7311	$261.73	$261.75	$261.70
7 purchase totals =	$1,241.72		$1,363.2194	$1,363.23	$1,363.30	$1,363.30