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	$112.82	7.702%	$121.5094	$121.51	$121.50	$121.50
Purchase #2	$154.51	10.724%	$171.0797	$171.08	$171.10	$171.10
Purchase #3	$220.92	7.562%	$237.626	$237.63	$237.65	$237.60
Purchase #4	$184.79	3.654%	$191.5422	$191.54	$191.55	$191.50
Purchase #5	$113.81	11.774%	$127.21	$127.21	$127.20	$127.20
Purchase #6	$198.52	12.180%	$222.6997	$222.70	$222.70	$222.70
Purchase #7	$79.35	9.463%	$86.8589	$86.86	$86.85	$86.90
7 purchase totals =	$1,064.72		$1,158.5259	$1,158.53	$1,158.55	$1,158.50