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	$82.39	5.148%	$86.6314	$86.63	$86.65	$86.60
Purchase #2	$92.42	4.600%	$96.6713	$96.67	$96.65	$96.70
Purchase #3	$230.62	10.644%	$255.1672	$255.17	$255.15	$255.20
Purchase #4	$150.75	7.749%	$162.4316	$162.43	$162.45	$162.40
Purchase #5	$100.48	9.808%	$110.3351	$110.34	$110.35	$110.30
Purchase #6	$244.48	9.817%	$268.4806	$268.48	$268.50	$268.50
Purchase #7	$21.92	13.758%	$24.9358	$24.94	$24.95	$24.90
7 purchase totals =	$923.06		$1,004.6530	$1,004.66	$1,004.70	$1,004.60