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	$119.40	4.533%	$124.8124	$124.81	$124.80	$124.80
Purchase #2	$88.49	4.644%	$92.5995	$92.60	$92.60	$92.60
Purchase #3	$96.25	4.482%	$100.5639	$100.56	$100.55	$100.60
Purchase #4	$142.40	12.283%	$159.891	$159.89	$159.90	$159.90
Purchase #5	$236.89	9.210%	$258.7076	$258.71	$258.70	$258.70
Purchase #6	$60.85	7.302%	$65.2933	$65.29	$65.30	$65.30
Purchase #7	$164.41	6.631%	$175.312	$175.31	$175.30	$175.30
7 purchase totals =	$908.69		$977.1797	$977.17	$977.15	$977.20