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	$118.67	4.360%	$123.844	$123.84	$123.85	$123.80
Purchase #2	$211.86	5.476%	$223.4615	$223.46	$223.45	$223.50
Purchase #3	$45.47	11.824%	$50.8464	$50.85	$50.85	$50.80
Purchase #4	$35.34	4.678%	$36.9932	$36.99	$37.00	$37.00
Purchase #5	$5.84	4.752%	$6.1175	$6.12	$6.10	$6.10
Purchase #6	$92.46	7.657%	$99.5397	$99.54	$99.55	$99.50
Purchase #7	$132.39	4.366%	$138.1701	$138.17	$138.15	$138.20
7 purchase totals =	$642.03		$678.9724	$678.97	$678.95	$678.90