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	$44.26	3.864%	$45.9702	$45.97	$45.95	$46.00
Purchase #2	$32.94	7.621%	$35.4504	$35.45	$35.45	$35.50
Purchase #3	$236.34	13.778%	$268.9029	$268.90	$268.90	$268.90
Purchase #4	$158.87	9.237%	$173.5448	$173.54	$173.55	$173.50
Purchase #5	$47.28	6.619%	$50.4095	$50.41	$50.40	$50.40
Purchase #6	$98.35	5.462%	$103.7219	$103.72	$103.70	$103.70
Purchase #7	$105.61	3.547%	$109.356	$109.36	$109.35	$109.40
7 purchase totals =	$723.65		$787.3557	$787.35	$787.30	$787.40