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	$118.32	5.152%	$124.4158	$124.42	$124.40	$124.40
Purchase #2	$93.73	8.256%	$101.4683	$101.47	$101.45	$101.50
Purchase #3	$151.85	12.116%	$170.2481	$170.25	$170.25	$170.20
Purchase #4	$218.62	3.294%	$225.8213	$225.82	$225.80	$225.80
Purchase #5	$100.80	11.279%	$112.1692	$112.17	$112.15	$112.20
Purchase #6	$195.64	13.736%	$222.5131	$222.51	$222.50	$222.50
Purchase #7	$169.43	11.372%	$188.6976	$188.70	$188.70	$188.70
7 purchase totals =	$1,048.39		$1,145.3334	$1,145.34	$1,145.25	$1,145.30