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	$42.72	6.729%	$45.5946	$45.59	$45.60	$45.60
Purchase #2	$147.89	10.164%	$162.9215	$162.92	$162.90	$162.90
Purchase #3	$59.98	10.262%	$66.1351	$66.14	$66.15	$66.10
Purchase #4	$28.34	4.712%	$29.6754	$29.68	$29.70	$29.70
Purchase #5	$211.43	9.773%	$232.0931	$232.09	$232.10	$232.10
Purchase #6	$227.96	7.613%	$245.3146	$245.31	$245.30	$245.30
Purchase #7	$179.95	8.122%	$194.5655	$194.57	$194.55	$194.60
7 purchase totals =	$898.27		$976.2998	$976.30	$976.30	$976.30