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	$99.30	4.191%	$103.4617	$103.46	$103.45	$103.50
Purchase #2	$206.70	7.437%	$222.0723	$222.07	$222.05	$222.10
Purchase #3	$65.56	8.443%	$71.0952	$71.10	$71.10	$71.10
Purchase #4	$163.35	7.807%	$176.1027	$176.10	$176.10	$176.10
Purchase #5	$37.42	10.104%	$41.2009	$41.20	$41.20	$41.20
Purchase #6	$192.76	9.578%	$211.2226	$211.22	$211.20	$211.20
Purchase #7	$165.79	13.129%	$187.5566	$187.56	$187.55	$187.60
7 purchase totals =	$930.88		$1,012.7120	$1,012.71	$1,012.65	$1,012.80