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	$228.96	11.615%	$255.5537	$255.55	$255.55	$255.60
Purchase #2	$240.89	12.130%	$270.11	$270.11	$270.10	$270.10
Purchase #3	$186.34	12.859%	$210.3015	$210.30	$210.30	$210.30
Purchase #4	$36.64	10.266%	$40.4015	$40.40	$40.40	$40.40
Purchase #5	$60.73	10.661%	$67.2044	$67.20	$67.20	$67.20
Purchase #6	$44.63	11.401%	$49.7183	$49.72	$49.70	$49.70
Purchase #7	$198.43	6.829%	$211.9808	$211.98	$212.00	$212.00
7 purchase totals =	$996.62		$1,105.2702	$1,105.26	$1,105.25	$1,105.30