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	$245.69	12.353%	$276.0401	$276.04	$276.05	$276.00
Purchase #2	$80.32	8.389%	$87.058	$87.06	$87.05	$87.10
Purchase #3	$105.69	12.224%	$118.6095	$118.61	$118.60	$118.60
Purchase #4	$50.58	5.359%	$53.2906	$53.29	$53.30	$53.30
Purchase #5	$12.27	4.815%	$12.8608	$12.86	$12.85	$12.90
Purchase #6	$108.98	13.729%	$123.9419	$123.94	$123.95	$123.90
Purchase #7	$147.98	3.549%	$153.2318	$153.23	$153.25	$153.20
7 purchase totals =	$751.51		$825.0327	$825.03	$825.05	$825.00