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	$237.76	5.349%	$250.4778	$250.48	$250.50	$250.50
Purchase #2	$152.56	13.301%	$172.852	$172.85	$172.85	$172.90
Purchase #3	$216.81	12.292%	$243.4603	$243.46	$243.45	$243.50
Purchase #4	$48.47	5.547%	$51.1586	$51.16	$51.15	$51.20
Purchase #5	$96.40	3.727%	$99.9928	$99.99	$100.00	$100.00
Purchase #6	$58.48	8.760%	$63.6028	$63.60	$63.60	$63.60
Purchase #7	$172.96	9.198%	$188.8689	$188.87	$188.85	$188.90
7 purchase totals =	$983.44		$1,070.4132	$1,070.41	$1,070.40	$1,070.60