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	$207.54	9.743%	$227.7606	$227.76	$227.75	$227.80
Purchase #2	$169.79	12.143%	$190.4076	$190.41	$190.40	$190.40
Purchase #3	$138.31	8.555%	$150.1424	$150.14	$150.15	$150.10
Purchase #4	$18.70	12.552%	$21.0472	$21.05	$21.05	$21.00
Purchase #5	$99.64	6.476%	$106.0927	$106.09	$106.10	$106.10
Purchase #6	$230.53	5.543%	$243.3083	$243.31	$243.30	$243.30
Purchase #7	$178.64	5.450%	$188.3759	$188.38	$188.40	$188.40
7 purchase totals =	$1,043.15		$1,127.1347	$1,127.14	$1,127.15	$1,127.10