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	$152.76	5.267%	$160.8059	$160.81	$160.80	$160.80
Purchase #2	$247.93	6.571%	$264.2215	$264.22	$264.20	$264.20
Purchase #3	$144.38	7.492%	$155.1969	$155.20	$155.20	$155.20
Purchase #4	$211.31	11.834%	$236.3164	$236.32	$236.30	$236.30
Purchase #5	$250.31	7.290%	$268.5576	$268.56	$268.55	$268.60
Purchase #6	$148.29	6.641%	$158.1379	$158.14	$158.15	$158.10
Purchase #7	$40.83	11.221%	$45.4115	$45.41	$45.40	$45.40
7 purchase totals =	$1,195.81		$1,288.6477	$1,288.66	$1,288.60	$1,288.60