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	$78.28	10.776%	$86.7155	$86.72	$86.70	$86.70
Purchase #2	$35.55	6.152%	$37.737	$37.74	$37.75	$37.70
Purchase #3	$136.64	13.128%	$154.5781	$154.58	$154.60	$154.60
Purchase #4	$99.42	11.424%	$110.7777	$110.78	$110.80	$110.80
Purchase #5	$137.86	8.392%	$149.4292	$149.43	$149.45	$149.40
Purchase #6	$245.59	3.665%	$254.5909	$254.59	$254.60	$254.60
Purchase #7	$88.32	12.475%	$99.3379	$99.34	$99.35	$99.30
7 purchase totals =	$821.66		$893.1663	$893.18	$893.25	$893.10