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	$119.52	7.848%	$128.8999	$128.90	$128.90	$128.90
Purchase #2	$249.77	11.810%	$279.2678	$279.27	$279.25	$279.30
Purchase #3	$169.53	5.275%	$178.4727	$178.47	$178.45	$178.50
Purchase #4	$124.66	4.717%	$130.5402	$130.54	$130.55	$130.50
Purchase #5	$83.31	10.501%	$92.0584	$92.06	$92.05	$92.10
Purchase #6	$144.28	12.533%	$162.3626	$162.36	$162.35	$162.40
Purchase #7	$157.81	13.170%	$178.5936	$178.59	$178.60	$178.60
7 purchase totals =	$1,048.88		$1,150.1952	$1,150.19	$1,150.15	$1,150.30