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	$216.70	13.506%	$245.9675	$245.97	$245.95	$246.00
Purchase #2	$152.60	12.171%	$171.1729	$171.17	$171.15	$171.20
Purchase #3	$38.39	7.645%	$41.3249	$41.32	$41.30	$41.30
Purchase #4	$19.72	10.369%	$21.7648	$21.76	$21.75	$21.80
Purchase #5	$83.44	7.284%	$89.5178	$89.52	$89.50	$89.50
Purchase #6	$125.29	6.373%	$133.2747	$133.27	$133.25	$133.30
Purchase #7	$52.91	13.284%	$59.9386	$59.94	$59.95	$59.90
7 purchase totals =	$689.05		$762.9612	$762.95	$762.85	$763.00