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	$64.50	5.753%	$68.2107	$68.21	$68.20	$68.20
Purchase #2	$104.51	13.301%	$118.4109	$118.41	$118.40	$118.40
Purchase #3	$169.82	3.400%	$175.5939	$175.59	$175.60	$175.60
Purchase #4	$229.63	11.521%	$256.0857	$256.09	$256.10	$256.10
Purchase #5	$219.86	8.336%	$238.1875	$238.19	$238.20	$238.20
Purchase #6	$152.44	7.873%	$164.4416	$164.44	$164.45	$164.40
Purchase #7	$105.64	5.773%	$111.7386	$111.74	$111.75	$111.70
7 purchase totals =	$1,046.40		$1,132.6689	$1,132.67	$1,132.70	$1,132.60