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	$152.29	8.391%	$165.0687	$165.07	$165.05	$165.10
Purchase #2	$54.56	3.103%	$56.253	$56.25	$56.25	$56.30
Purchase #3	$162.85	11.767%	$182.0126	$182.01	$182.00	$182.00
Purchase #4	$54.79	9.200%	$59.8307	$59.83	$59.85	$59.80
Purchase #5	$205.35	4.272%	$214.1226	$214.12	$214.10	$214.10
Purchase #6	$13.46	13.138%	$15.2284	$15.23	$15.25	$15.20
Purchase #7	$204.50	4.648%	$214.0052	$214.01	$214.00	$214.00
7 purchase totals =	$847.80		$906.5212	$906.52	$906.50	$906.50