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	$171.67	7.448%	$184.456	$184.46	$184.45	$184.50
Purchase #2	$48.28	12.459%	$54.2952	$54.30	$54.30	$54.30
Purchase #3	$35.49	11.284%	$39.4947	$39.49	$39.50	$39.50
Purchase #4	$216.82	7.502%	$233.0858	$233.09	$233.10	$233.10
Purchase #5	$30.43	11.347%	$33.8829	$33.88	$33.90	$33.90
Purchase #6	$227.31	5.847%	$240.6008	$240.60	$240.60	$240.60
Purchase #7	$225.84	12.761%	$254.6594	$254.66	$254.65	$254.70
7 purchase totals =	$955.84		$1,040.4748	$1,040.48	$1,040.50	$1,040.60