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	$131.30	11.538%	$146.4494	$146.45	$146.45	$146.40
Purchase #2	$191.69	13.236%	$217.0621	$217.06	$217.05	$217.10
Purchase #3	$176.61	13.435%	$200.3376	$200.34	$200.35	$200.30
Purchase #4	$120.89	8.435%	$131.0871	$131.09	$131.10	$131.10
Purchase #5	$162.91	9.342%	$178.1291	$178.13	$178.15	$178.10
Purchase #6	$145.37	13.668%	$165.2392	$165.24	$165.25	$165.20
Purchase #7	$43.91	6.591%	$46.8041	$46.80	$46.80	$46.80
7 purchase totals =	$972.68		$1,085.1086	$1,085.11	$1,085.15	$1,085.00