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	$233.84	4.520%	$244.4096	$244.41	$244.40	$244.40
Purchase #2	$72.96	4.552%	$76.2811	$76.28	$76.30	$76.30
Purchase #3	$147.78	9.505%	$161.8265	$161.83	$161.85	$161.80
Purchase #4	$204.36	8.721%	$222.1822	$222.18	$222.20	$222.20
Purchase #5	$29.78	10.378%	$32.8706	$32.87	$32.85	$32.90
Purchase #6	$30.90	7.266%	$33.1452	$33.15	$33.15	$33.10
Purchase #7	$212.80	12.215%	$238.7935	$238.79	$238.80	$238.80
7 purchase totals =	$932.42		$1,009.5087	$1,009.51	$1,009.55	$1,009.50