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	$82.37	7.475%	$88.5272	$88.53	$88.55	$88.50
Purchase #2	$69.52	11.588%	$77.576	$77.58	$77.60	$77.60
Purchase #3	$29.25	11.132%	$32.5061	$32.51	$32.50	$32.50
Purchase #4	$84.39	6.505%	$89.8796	$89.88	$89.90	$89.90
Purchase #5	$6.28	7.435%	$6.7469	$6.75	$6.75	$6.70
Purchase #6	$51.33	13.172%	$58.0912	$58.09	$58.10	$58.10
Purchase #7	$80.71	11.465%	$89.9634	$89.96	$89.95	$90.00
7 purchase totals =	$403.85		$443.2904	$443.30	$443.35	$443.30