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	$45.29	6.230%	$48.1116	$48.11	$48.10	$48.10
Purchase #2	$57.26	4.562%	$59.8722	$59.87	$59.85	$59.90
Purchase #3	$81.65	4.664%	$85.4582	$85.46	$85.45	$85.50
Purchase #4	$119.95	6.566%	$127.8259	$127.83	$127.85	$127.80
Purchase #5	$25.42	5.698%	$26.8684	$26.87	$26.85	$26.90
Purchase #6	$148.97	13.743%	$169.4429	$169.44	$169.45	$169.40
Purchase #7	$247.46	7.230%	$265.3514	$265.35	$265.35	$265.40
7 purchase totals =	$726.00		$782.9306	$782.93	$782.90	$783.00