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	$47.51	12.623%	$53.5072	$53.51	$53.50	$53.50
Purchase #2	$226.35	13.505%	$256.9186	$256.92	$256.90	$256.90
Purchase #3	$249.97	12.778%	$281.9112	$281.91	$281.90	$281.90
Purchase #4	$102.92	3.754%	$106.7836	$106.78	$106.80	$106.80
Purchase #5	$66.53	7.369%	$71.4326	$71.43	$71.45	$71.40
Purchase #6	$142.29	4.336%	$148.4597	$148.46	$148.45	$148.50
Purchase #7	$129.97	8.850%	$141.4723	$141.47	$141.45	$141.50
7 purchase totals =	$965.54		$1,060.4852	$1,060.48	$1,060.45	$1,060.50