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	$65.28	7.625%	$70.2576	$70.26	$70.25	$70.30
Purchase #2	$146.37	11.210%	$162.7781	$162.78	$162.80	$162.80
Purchase #3	$36.90	11.819%	$41.2612	$41.26	$41.25	$41.30
Purchase #4	$118.49	7.490%	$127.3649	$127.36	$127.35	$127.40
Purchase #5	$42.59	6.647%	$45.421	$45.42	$45.40	$45.40
Purchase #6	$79.28	13.384%	$89.8908	$89.89	$89.90	$89.90
Purchase #7	$114.64	9.429%	$125.4494	$125.45	$125.45	$125.40
7 purchase totals =	$603.55		$662.4230	$662.42	$662.40	$662.50