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	$114.87	11.668%	$128.273	$128.27	$128.25	$128.30
Purchase #2	$62.49	10.670%	$69.1577	$69.16	$69.15	$69.20
Purchase #3	$138.79	8.277%	$150.2776	$150.28	$150.30	$150.30
Purchase #4	$241.90	3.490%	$250.3423	$250.34	$250.35	$250.30
Purchase #5	$227.28	11.822%	$254.149	$254.15	$254.15	$254.10
Purchase #6	$138.39	10.801%	$153.3375	$153.34	$153.35	$153.30
Purchase #7	$131.63	11.518%	$146.7911	$146.79	$146.80	$146.80
7 purchase totals =	$1,055.35		$1,152.3282	$1,152.33	$1,152.35	$1,152.30