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	$42.31	12.106%	$47.432	$47.43	$47.45	$47.40
Purchase #2	$73.98	6.609%	$78.8693	$78.87	$78.85	$78.90
Purchase #3	$7.72	13.712%	$8.7786	$8.78	$8.80	$8.80
Purchase #4	$213.64	4.129%	$222.4612	$222.46	$222.45	$222.50
Purchase #5	$85.77	11.674%	$95.7828	$95.78	$95.80	$95.80
Purchase #6	$106.36	9.310%	$116.2621	$116.26	$116.25	$116.30
Purchase #7	$111.69	9.288%	$122.0638	$122.06	$122.05	$122.10
7 purchase totals =	$641.47		$691.6498	$691.64	$691.65	$691.80