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	$102.48	8.775%	$111.4726	$111.47	$111.45	$111.50
Purchase #2	$93.91	11.817%	$105.0073	$105.01	$105.00	$105.00
Purchase #3	$127.55	12.345%	$143.296	$143.30	$143.30	$143.30
Purchase #4	$148.95	11.607%	$166.2386	$166.24	$166.25	$166.20
Purchase #5	$63.96	9.616%	$70.1104	$70.11	$70.10	$70.10
Purchase #6	$84.31	5.123%	$88.6292	$88.63	$88.65	$88.60
Purchase #7	$64.64	10.548%	$71.4582	$71.46	$71.45	$71.50
7 purchase totals =	$685.80		$756.2123	$756.22	$756.20	$756.20