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	$119.83	7.718%	$129.0785	$129.08	$129.10	$129.10
Purchase #2	$130.61	4.294%	$136.2184	$136.22	$136.20	$136.20
Purchase #3	$42.27	7.847%	$45.5869	$45.59	$45.60	$45.60
Purchase #4	$43.53	11.212%	$48.4106	$48.41	$48.40	$48.40
Purchase #5	$182.64	6.406%	$194.3399	$194.34	$194.35	$194.30
Purchase #6	$216.76	7.766%	$233.5936	$233.59	$233.60	$233.60
Purchase #7	$100.42	4.653%	$105.0925	$105.09	$105.10	$105.10
7 purchase totals =	$836.06		$892.3204	$892.32	$892.35	$892.30