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	$172.33	10.515%	$190.4505	$190.45	$190.45	$190.50
Purchase #2	$37.72	11.299%	$41.982	$41.98	$42.00	$42.00
Purchase #3	$247.73	13.312%	$280.7078	$280.71	$280.70	$280.70
Purchase #4	$31.63	4.725%	$33.1245	$33.12	$33.10	$33.10
Purchase #5	$237.78	11.414%	$264.9202	$264.92	$264.90	$264.90
Purchase #6	$150.57	12.620%	$169.5719	$169.57	$169.55	$169.60
Purchase #7	$18.73	12.613%	$21.0924	$21.09	$21.10	$21.10
7 purchase totals =	$896.49		$1,001.8493	$1,001.84	$1,001.80	$1,001.90