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	$158.31	9.490%	$173.3336	$173.33	$173.35	$173.30
Purchase #2	$87.93	11.649%	$98.173	$98.17	$98.15	$98.20
Purchase #3	$159.46	13.454%	$180.9137	$180.91	$180.90	$180.90
Purchase #4	$131.28	9.750%	$144.0798	$144.08	$144.10	$144.10
Purchase #5	$103.61	7.439%	$111.3175	$111.32	$111.30	$111.30
Purchase #6	$42.70	12.245%	$47.9286	$47.93	$47.95	$47.90
Purchase #7	$38.56	7.555%	$41.4732	$41.47	$41.45	$41.50
7 purchase totals =	$721.85		$797.2194	$797.21	$797.20	$797.20