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	$56.84	4.303%	$59.2858	$59.29	$59.30	$59.30
Purchase #2	$168.87	12.828%	$190.5326	$190.53	$190.55	$190.50
Purchase #3	$33.31	10.308%	$36.7436	$36.74	$36.75	$36.70
Purchase #4	$166.62	9.367%	$182.2273	$182.23	$182.25	$182.20
Purchase #5	$234.73	4.552%	$245.4149	$245.41	$245.40	$245.40
Purchase #6	$8.93	13.387%	$10.1255	$10.13	$10.15	$10.10
Purchase #7	$94.77	7.485%	$101.8635	$101.86	$101.85	$101.90
7 purchase totals =	$764.07		$826.1932	$826.19	$826.25	$826.10