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	$133.37	10.303%	$147.1111	$147.11	$147.10	$147.10
Purchase #2	$50.46	10.624%	$55.8209	$55.82	$55.80	$55.80
Purchase #3	$137.89	13.402%	$156.37	$156.37	$156.35	$156.40
Purchase #4	$52.55	13.762%	$59.7819	$59.78	$59.80	$59.80
Purchase #5	$161.59	7.679%	$173.9985	$174.00	$174.00	$174.00
Purchase #6	$57.83	9.310%	$63.214	$63.21	$63.20	$63.20
Purchase #7	$87.81	9.479%	$96.1335	$96.13	$96.15	$96.10
7 purchase totals =	$681.50		$752.4299	$752.42	$752.40	$752.40