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	$55.28	7.194%	$59.2568	$59.26	$59.25	$59.30
Purchase #2	$90.66	9.732%	$99.483	$99.48	$99.50	$99.50
Purchase #3	$121.49	10.401%	$134.1262	$134.13	$134.15	$134.10
Purchase #4	$31.62	4.336%	$32.991	$32.99	$33.00	$33.00
Purchase #5	$35.87	9.731%	$39.3605	$39.36	$39.35	$39.40
Purchase #6	$37.65	11.336%	$41.918	$41.92	$41.90	$41.90
Purchase #7	$183.55	7.794%	$197.8559	$197.86	$197.85	$197.90
7 purchase totals =	$556.12		$604.9914	$605.00	$605.00	$605.10