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	$150.87	5.395%	$159.0094	$159.01	$159.00	$159.00
Purchase #2	$224.77	8.178%	$243.1517	$243.15	$243.15	$243.20
Purchase #3	$40.74	5.104%	$42.8194	$42.82	$42.80	$42.80
Purchase #4	$11.31	3.378%	$11.6921	$11.69	$11.70	$11.70
Purchase #5	$33.83	4.358%	$35.3043	$35.30	$35.30	$35.30
Purchase #6	$69.26	5.243%	$72.8913	$72.89	$72.90	$72.90
Purchase #7	$179.27	5.625%	$189.3539	$189.35	$189.35	$189.40
7 purchase totals =	$710.05		$754.2221	$754.21	$754.20	$754.30