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	$188.84	11.654%	$210.8474	$210.85	$210.85	$210.80
Purchase #2	$90.40	10.365%	$99.77	$99.77	$99.75	$99.80
Purchase #3	$138.93	9.872%	$152.6452	$152.65	$152.65	$152.60
Purchase #4	$221.70	13.609%	$251.8712	$251.87	$251.85	$251.90
Purchase #5	$71.88	11.687%	$80.2806	$80.28	$80.30	$80.30
Purchase #6	$6.52	10.671%	$7.2157	$7.22	$7.20	$7.20
Purchase #7	$150.52	12.853%	$169.8663	$169.87	$169.85	$169.90
7 purchase totals =	$868.79		$972.4964	$972.51	$972.45	$972.50