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	$213.58	7.235%	$229.0325	$229.03	$229.05	$229.00
Purchase #2	$88.50	11.203%	$98.4147	$98.41	$98.40	$98.40
Purchase #3	$128.54	8.453%	$139.4055	$139.41	$139.40	$139.40
Purchase #4	$87.47	13.495%	$99.2741	$99.27	$99.25	$99.30
Purchase #5	$34.82	8.243%	$37.6902	$37.69	$37.70	$37.70
Purchase #6	$98.39	11.357%	$109.5642	$109.56	$109.55	$109.60
Purchase #7	$94.26	8.119%	$101.913	$101.91	$101.90	$101.90
7 purchase totals =	$745.56		$815.2942	$815.28	$815.25	$815.30