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	$83.38	7.677%	$89.7811	$89.78	$89.80	$89.80
Purchase #2	$52.48	4.539%	$54.8621	$54.86	$54.85	$54.90
Purchase #3	$250.44	6.192%	$265.9472	$265.95	$265.95	$265.90
Purchase #4	$98.88	11.754%	$110.5024	$110.50	$110.50	$110.50
Purchase #5	$147.72	8.848%	$160.7903	$160.79	$160.80	$160.80
Purchase #6	$87.69	9.451%	$95.9776	$95.98	$96.00	$96.00
Purchase #7	$242.66	6.775%	$259.1002	$259.10	$259.10	$259.10
7 purchase totals =	$963.25		$1,036.9609	$1,036.96	$1,037.00	$1,037.00