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	$29.84	11.369%	$33.2325	$33.23	$33.25	$33.20
Purchase #2	$11.64	5.827%	$12.3183	$12.32	$12.30	$12.30
Purchase #3	$55.55	7.292%	$59.6007	$59.60	$59.60	$59.60
Purchase #4	$16.70	11.365%	$18.598	$18.60	$18.60	$18.60
Purchase #5	$51.31	7.860%	$55.343	$55.34	$55.35	$55.30
Purchase #6	$9.56	10.702%	$10.5831	$10.58	$10.60	$10.60
Purchase #7	$94.87	11.696%	$105.966	$105.97	$105.95	$106.00
7 purchase totals =	$269.47		$295.6416	$295.64	$295.65	$295.60