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	$59.81	3.470%	$61.8854	$61.89	$61.90	$61.90
Purchase #2	$91.26	5.108%	$95.9216	$95.92	$95.90	$95.90
Purchase #3	$246.71	3.779%	$256.0332	$256.03	$256.05	$256.00
Purchase #4	$33.30	11.174%	$37.0209	$37.02	$37.00	$37.00
Purchase #5	$18.30	11.532%	$20.4104	$20.41	$20.40	$20.40
Purchase #6	$164.82	3.254%	$170.1832	$170.18	$170.20	$170.20
Purchase #7	$139.37	9.542%	$152.6687	$152.67	$152.65	$152.70
7 purchase totals =	$753.57		$794.1234	$794.12	$794.10	$794.10