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	$168.64	3.476%	$174.5019	$174.50	$174.50	$174.50
Purchase #2	$105.66	12.669%	$119.0461	$119.05	$119.05	$119.00
Purchase #3	$158.72	4.225%	$165.4259	$165.43	$165.45	$165.40
Purchase #4	$220.63	13.862%	$251.2137	$251.21	$251.20	$251.20
Purchase #5	$145.26	11.739%	$162.3121	$162.31	$162.30	$162.30
Purchase #6	$72.68	5.202%	$76.4608	$76.46	$76.45	$76.50
Purchase #7	$65.38	11.447%	$72.864	$72.86	$72.85	$72.90
7 purchase totals =	$936.97		$1,021.8245	$1,021.82	$1,021.80	$1,021.80