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	$60.89	5.672%	$64.3437	$64.34	$64.35	$64.30
Purchase #2	$133.31	13.716%	$151.5948	$151.59	$151.60	$151.60
Purchase #3	$219.35	11.753%	$245.1302	$245.13	$245.15	$245.10
Purchase #4	$64.41	9.349%	$70.4317	$70.43	$70.45	$70.40
Purchase #5	$226.33	7.341%	$242.9449	$242.94	$242.95	$242.90
Purchase #6	$160.35	4.256%	$167.1745	$167.17	$167.15	$167.20
Purchase #7	$202.56	6.375%	$215.4732	$215.47	$215.45	$215.50
7 purchase totals =	$1,067.20		$1,157.0930	$1,157.07	$1,157.10	$1,157.00