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	$94.68	11.528%	$105.5947	$105.59	$105.60	$105.60
Purchase #2	$245.59	7.734%	$264.5839	$264.58	$264.60	$264.60
Purchase #3	$229.90	6.471%	$244.7768	$244.78	$244.80	$244.80
Purchase #4	$105.54	3.773%	$109.522	$109.52	$109.50	$109.50
Purchase #5	$217.61	12.747%	$245.3487	$245.35	$245.35	$245.30
Purchase #6	$90.84	5.213%	$95.5755	$95.58	$95.60	$95.60
Purchase #7	$139.90	9.240%	$152.8268	$152.83	$152.85	$152.80
7 purchase totals =	$1,124.06		$1,218.2284	$1,218.23	$1,218.30	$1,218.20