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	$140.78	12.451%	$158.3085	$158.31	$158.30	$158.30
Purchase #2	$141.37	5.414%	$149.0238	$149.02	$149.00	$149.00
Purchase #3	$88.92	7.310%	$95.4201	$95.42	$95.40	$95.40
Purchase #4	$137.74	6.295%	$146.4107	$146.41	$146.40	$146.40
Purchase #5	$248.53	4.176%	$258.9086	$258.91	$258.90	$258.90
Purchase #6	$242.26	11.218%	$269.4367	$269.44	$269.45	$269.40
Purchase #7	$200.96	11.109%	$223.2846	$223.28	$223.30	$223.30
7 purchase totals =	$1,200.56		$1,300.7930	$1,300.79	$1,300.75	$1,300.70