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	$218.54	3.246%	$225.6338	$225.63	$225.65	$225.60
Purchase #2	$232.69	3.857%	$241.6649	$241.66	$241.65	$241.70
Purchase #3	$98.69	5.263%	$103.8841	$103.88	$103.90	$103.90
Purchase #4	$60.34	6.605%	$64.3255	$64.33	$64.35	$64.30
Purchase #5	$85.97	3.611%	$89.0744	$89.07	$89.05	$89.10
Purchase #6	$59.89	3.554%	$62.0185	$62.02	$62.00	$62.00
Purchase #7	$202.67	4.488%	$211.7658	$211.77	$211.75	$211.80
7 purchase totals =	$958.79		$998.3670	$998.36	$998.35	$998.40