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	$137.34	10.470%	$151.7195	$151.72	$151.70	$151.70
Purchase #2	$53.56	11.345%	$59.6364	$59.64	$59.65	$59.60
Purchase #3	$231.50	10.657%	$256.171	$256.17	$256.15	$256.20
Purchase #4	$120.58	5.355%	$127.0371	$127.04	$127.05	$127.00
Purchase #5	$117.49	7.814%	$126.6707	$126.67	$126.65	$126.70
Purchase #6	$154.92	7.522%	$166.5731	$166.57	$166.55	$166.60
Purchase #7	$145.78	12.550%	$164.0754	$164.08	$164.10	$164.10
7 purchase totals =	$961.17		$1,051.8832	$1,051.89	$1,051.85	$1,051.90