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	$180.45	5.555%	$190.474	$190.47	$190.45	$190.50
Purchase #2	$6.33	11.696%	$7.0704	$7.07	$7.05	$7.10
Purchase #3	$113.35	6.318%	$120.5115	$120.51	$120.50	$120.50
Purchase #4	$36.48	12.244%	$40.9466	$40.95	$40.95	$40.90
Purchase #5	$241.37	12.398%	$271.2951	$271.30	$271.30	$271.30
Purchase #6	$183.98	4.247%	$191.7936	$191.79	$191.80	$191.80
Purchase #7	$179.29	5.230%	$188.6669	$188.67	$188.65	$188.70
7 purchase totals =	$941.25		$1,010.7581	$1,010.76	$1,010.70	$1,010.80