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	$143.92	6.301%	$152.9884	$152.99	$153.00	$153.00
Purchase #2	$53.43	10.664%	$59.1278	$59.13	$59.15	$59.10
Purchase #3	$166.59	9.139%	$181.8147	$181.81	$181.80	$181.80
Purchase #4	$57.81	9.603%	$63.3615	$63.36	$63.35	$63.40
Purchase #5	$53.83	10.512%	$59.4886	$59.49	$59.50	$59.50
Purchase #6	$71.52	9.873%	$78.5812	$78.58	$78.60	$78.60
Purchase #7	$143.87	5.112%	$151.2246	$151.22	$151.20	$151.20
7 purchase totals =	$690.97		$746.5868	$746.58	$746.60	$746.60