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	$126.51	8.603%	$137.3937	$137.39	$137.40	$137.40
Purchase #2	$23.76	4.825%	$24.9064	$24.91	$24.90	$24.90
Purchase #3	$79.25	3.869%	$82.3162	$82.32	$82.30	$82.30
Purchase #4	$209.81	4.221%	$218.6661	$218.67	$218.65	$218.70
Purchase #5	$201.64	6.195%	$214.1316	$214.13	$214.15	$214.10
Purchase #6	$245.46	11.719%	$274.2255	$274.23	$274.25	$274.20
Purchase #7	$101.73	9.853%	$111.7535	$111.75	$111.75	$111.80
7 purchase totals =	$988.16		$1,063.3930	$1,063.40	$1,063.40	$1,063.40