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	$32.36	11.439%	$36.0617	$36.06	$36.05	$36.10
Purchase #2	$168.91	9.601%	$185.127	$185.13	$185.15	$185.10
Purchase #3	$67.35	11.167%	$74.871	$74.87	$74.85	$74.90
Purchase #4	$249.39	4.336%	$260.2036	$260.20	$260.20	$260.20
Purchase #5	$130.59	13.562%	$148.3006	$148.30	$148.30	$148.30
Purchase #6	$57.93	3.256%	$59.8162	$59.82	$59.80	$59.80
Purchase #7	$54.61	13.212%	$61.8251	$61.83	$61.85	$61.80
7 purchase totals =	$761.14		$826.2052	$826.21	$826.20	$826.20