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	$224.86	3.842%	$233.4991	$233.50	$233.50	$233.50
Purchase #2	$151.81	10.586%	$167.8806	$167.88	$167.90	$167.90
Purchase #3	$161.28	12.827%	$181.9674	$181.97	$181.95	$182.00
Purchase #4	$85.95	4.621%	$89.9217	$89.92	$89.90	$89.90
Purchase #5	$130.66	11.201%	$145.2952	$145.30	$145.30	$145.30
Purchase #6	$33.59	7.609%	$36.1459	$36.15	$36.15	$36.10
Purchase #7	$201.79	7.475%	$216.8738	$216.87	$216.85	$216.90
7 purchase totals =	$989.94		$1,071.5837	$1,071.59	$1,071.55	$1,071.60