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	$199.82	11.102%	$222.004	$222.00	$222.00	$222.00
Purchase #2	$188.87	6.333%	$200.8311	$200.83	$200.85	$200.80
Purchase #3	$130.75	13.343%	$148.196	$148.20	$148.20	$148.20
Purchase #4	$61.66	8.849%	$67.1163	$67.12	$67.10	$67.10
Purchase #5	$216.56	8.318%	$234.5735	$234.57	$234.55	$234.60
Purchase #6	$214.38	12.502%	$241.1818	$241.18	$241.20	$241.20
Purchase #7	$26.36	7.689%	$28.3868	$28.39	$28.40	$28.40
7 purchase totals =	$1,038.40		$1,142.2895	$1,142.29	$1,142.30	$1,142.30