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	$76.27	13.753%	$86.7594	$86.76	$86.75	$86.80
Purchase #2	$19.30	9.624%	$21.1574	$21.16	$21.15	$21.20
Purchase #3	$237.39	13.636%	$269.7605	$269.76	$269.75	$269.80
Purchase #4	$227.57	11.582%	$253.9272	$253.93	$253.95	$253.90
Purchase #5	$37.26	13.691%	$42.3613	$42.36	$42.35	$42.40
Purchase #6	$142.41	5.830%	$150.7125	$150.71	$150.70	$150.70
Purchase #7	$240.86	4.413%	$251.4892	$251.49	$251.50	$251.50
7 purchase totals =	$981.06		$1,076.1675	$1,076.17	$1,076.15	$1,076.30