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	$159.66	9.302%	$174.5116	$174.51	$174.50	$174.50
Purchase #2	$162.38	11.783%	$181.5132	$181.51	$181.50	$181.50
Purchase #3	$163.57	10.443%	$180.6516	$180.65	$180.65	$180.70
Purchase #4	$79.36	4.742%	$83.1233	$83.12	$83.10	$83.10
Purchase #5	$78.27	12.503%	$88.0561	$88.06	$88.05	$88.10
Purchase #6	$60.91	11.180%	$67.7197	$67.72	$67.70	$67.70
Purchase #7	$229.54	11.549%	$256.0496	$256.05	$256.05	$256.00
7 purchase totals =	$933.69		$1,031.6251	$1,031.62	$1,031.55	$1,031.60