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	$170.95	5.166%	$179.7813	$179.78	$179.80	$179.80
Purchase #2	$91.92	5.373%	$96.8589	$96.86	$96.85	$96.90
Purchase #3	$247.73	9.129%	$270.3453	$270.35	$270.35	$270.30
Purchase #4	$93.77	6.321%	$99.6972	$99.70	$99.70	$99.70
Purchase #5	$209.89	7.400%	$225.4219	$225.42	$225.40	$225.40
Purchase #6	$56.95	3.533%	$58.962	$58.96	$58.95	$59.00
Purchase #7	$104.97	7.110%	$112.4334	$112.43	$112.45	$112.40
7 purchase totals =	$976.18		$1,043.5000	$1,043.50	$1,043.50	$1,043.50