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	$50.52	12.365%	$56.7668	$56.77	$56.75	$56.80
Purchase #2	$223.95	11.232%	$249.1041	$249.10	$249.10	$249.10
Purchase #3	$145.76	13.348%	$165.216	$165.22	$165.20	$165.20
Purchase #4	$152.57	10.683%	$168.8691	$168.87	$168.85	$168.90
Purchase #5	$234.78	9.233%	$256.4572	$256.46	$256.45	$256.50
Purchase #6	$80.56	13.244%	$91.2294	$91.23	$91.25	$91.20
Purchase #7	$53.89	5.695%	$56.959	$56.96	$56.95	$57.00
7 purchase totals =	$942.03		$1,044.6016	$1,044.61	$1,044.55	$1,044.70