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	$216.59	6.873%	$231.4762	$231.48	$231.50	$231.50
Purchase #2	$236.65	11.542%	$263.9641	$263.96	$263.95	$264.00
Purchase #3	$182.41	7.736%	$196.5212	$196.52	$196.50	$196.50
Purchase #4	$141.48	4.438%	$147.7589	$147.76	$147.75	$147.80
Purchase #5	$223.86	13.761%	$254.6654	$254.67	$254.65	$254.70
Purchase #6	$72.30	13.824%	$82.2948	$82.29	$82.30	$82.30
Purchase #7	$119.26	3.121%	$122.9821	$122.98	$123.00	$123.00
7 purchase totals =	$1,192.55		$1,299.6627	$1,299.66	$1,299.65	$1,299.80