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	$237.99	6.697%	$253.9282	$253.93	$253.95	$253.90
Purchase #2	$91.25	10.419%	$100.7573	$100.76	$100.75	$100.80
Purchase #3	$151.56	13.264%	$171.6629	$171.66	$171.65	$171.70
Purchase #4	$195.86	7.803%	$211.143	$211.14	$211.15	$211.10
Purchase #5	$151.68	8.312%	$164.2876	$164.29	$164.30	$164.30
Purchase #6	$186.73	7.343%	$200.4416	$200.44	$200.45	$200.40
Purchase #7	$74.69	11.645%	$83.3877	$83.39	$83.40	$83.40
7 purchase totals =	$1,089.76		$1,185.6083	$1,185.61	$1,185.65	$1,185.60