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	$41.98	13.289%	$47.5587	$47.56	$47.55	$47.60
Purchase #2	$33.43	12.277%	$37.5342	$37.53	$37.55	$37.50
Purchase #3	$21.99	9.519%	$24.0832	$24.08	$24.10	$24.10
Purchase #4	$167.83	11.714%	$187.4896	$187.49	$187.50	$187.50
Purchase #5	$129.80	13.301%	$147.0647	$147.06	$147.05	$147.10
Purchase #6	$99.86	12.213%	$112.0559	$112.06	$112.05	$112.10
Purchase #7	$20.33	3.670%	$21.0761	$21.08	$21.10	$21.10
7 purchase totals =	$515.22		$576.8624	$576.86	$576.90	$577.00