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	$147.42	11.437%	$164.2804	$164.28	$164.30	$164.30
Purchase #2	$242.84	5.138%	$255.3171	$255.32	$255.30	$255.30
Purchase #3	$132.71	13.823%	$151.0545	$151.05	$151.05	$151.10
Purchase #4	$229.30	10.422%	$253.1976	$253.20	$253.20	$253.20
Purchase #5	$164.97	8.747%	$179.3999	$179.40	$179.40	$179.40
Purchase #6	$131.73	7.773%	$141.9694	$141.97	$141.95	$142.00
Purchase #7	$137.27	10.811%	$152.1103	$152.11	$152.10	$152.10
7 purchase totals =	$1,186.24		$1,297.3292	$1,297.33	$1,297.30	$1,297.40