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	$192.44	13.826%	$219.0468	$219.05	$219.05	$219.00
Purchase #2	$40.59	13.714%	$46.1565	$46.16	$46.15	$46.20
Purchase #3	$165.42	12.535%	$186.1554	$186.16	$186.15	$186.20
Purchase #4	$120.58	6.614%	$128.5552	$128.56	$128.55	$128.60
Purchase #5	$210.35	8.755%	$228.7661	$228.77	$228.75	$228.80
Purchase #6	$38.72	12.261%	$43.4675	$43.47	$43.45	$43.50
Purchase #7	$160.55	11.203%	$178.5364	$178.54	$178.55	$178.50
7 purchase totals =	$928.65		$1,030.6839	$1,030.71	$1,030.65	$1,030.80