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	$203.58	7.252%	$218.3436	$218.34	$218.35	$218.30
Purchase #2	$93.64	7.561%	$100.7201	$100.72	$100.70	$100.70
Purchase #3	$45.92	6.126%	$48.7331	$48.73	$48.75	$48.70
Purchase #4	$198.37	12.373%	$222.9143	$222.91	$222.90	$222.90
Purchase #5	$240.87	13.376%	$273.0888	$273.09	$273.10	$273.10
Purchase #6	$109.49	4.304%	$114.2024	$114.20	$114.20	$114.20
Purchase #7	$118.44	7.489%	$127.31	$127.31	$127.30	$127.30
7 purchase totals =	$1,010.31		$1,105.3123	$1,105.30	$1,105.30	$1,105.20