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	$185.70	5.263%	$195.4734	$195.47	$195.45	$195.50
Purchase #2	$55.59	7.769%	$59.9088	$59.91	$59.90	$59.90
Purchase #3	$42.93	8.254%	$46.4734	$46.47	$46.45	$46.50
Purchase #4	$49.67	10.771%	$55.02	$55.02	$55.00	$55.00
Purchase #5	$46.58	3.244%	$48.0911	$48.09	$48.10	$48.10
Purchase #6	$111.32	10.651%	$123.1767	$123.18	$123.20	$123.20
Purchase #7	$65.69	12.219%	$73.7167	$73.72	$73.70	$73.70
7 purchase totals =	$557.48		$601.8601	$601.86	$601.80	$601.90