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	$133.77	4.346%	$139.5836	$139.58	$139.60	$139.60
Purchase #2	$198.67	4.845%	$208.2956	$208.30	$208.30	$208.30
Purchase #3	$222.40	10.429%	$245.5941	$245.59	$245.60	$245.60
Purchase #4	$5.95	13.404%	$6.7475	$6.75	$6.75	$6.70
Purchase #5	$245.59	7.826%	$264.8099	$264.81	$264.80	$264.80
Purchase #6	$240.83	6.375%	$256.1829	$256.18	$256.20	$256.20
Purchase #7	$52.38	3.331%	$54.1248	$54.12	$54.10	$54.10
7 purchase totals =	$1,099.59		$1,175.3384	$1,175.33	$1,175.35	$1,175.30