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	$100.38	5.765%	$106.1669	$106.17	$106.15	$106.20
Purchase #2	$185.81	7.621%	$199.9706	$199.97	$199.95	$200.00
Purchase #3	$167.53	5.107%	$176.0858	$176.09	$176.10	$176.10
Purchase #4	$91.70	9.857%	$100.7389	$100.74	$100.75	$100.70
Purchase #5	$154.91	6.631%	$165.1821	$165.18	$165.20	$165.20
Purchase #6	$73.78	6.809%	$78.8037	$78.80	$78.80	$78.80
Purchase #7	$36.28	4.394%	$37.8741	$37.87	$37.85	$37.90
7 purchase totals =	$810.39		$864.8221	$864.82	$864.80	$864.90