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	$195.42	6.450%	$208.0246	$208.02	$208.00	$208.00
Purchase #2	$206.38	8.437%	$223.7923	$223.79	$223.80	$223.80
Purchase #3	$185.49	12.427%	$208.5408	$208.54	$208.55	$208.50
Purchase #4	$235.27	10.300%	$259.5028	$259.50	$259.50	$259.50
Purchase #5	$58.25	7.545%	$62.645	$62.65	$62.65	$62.60
Purchase #6	$212.57	4.857%	$222.8945	$222.89	$222.90	$222.90
Purchase #7	$21.91	11.623%	$24.4566	$24.46	$24.45	$24.50
7 purchase totals =	$1,115.29		$1,209.8566	$1,209.85	$1,209.85	$1,209.80