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	$64.28	10.850%	$71.2544	$71.25	$71.25	$71.30
Purchase #2	$241.42	11.502%	$269.1881	$269.19	$269.20	$269.20
Purchase #3	$85.66	10.660%	$94.7914	$94.79	$94.80	$94.80
Purchase #4	$88.94	11.470%	$99.1414	$99.14	$99.15	$99.10
Purchase #5	$60.42	3.185%	$62.3444	$62.34	$62.35	$62.30
Purchase #6	$225.85	10.603%	$249.7969	$249.80	$249.80	$249.80
Purchase #7	$82.88	4.129%	$86.3021	$86.30	$86.30	$86.30
7 purchase totals =	$849.45		$932.8187	$932.81	$932.85	$932.80