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	$48.50	8.110%	$52.4334	$52.43	$52.45	$52.40
Purchase #2	$182.38	3.384%	$188.5517	$188.55	$188.55	$188.60
Purchase #3	$222.85	9.432%	$243.8692	$243.87	$243.85	$243.90
Purchase #4	$145.39	7.793%	$156.7202	$156.72	$156.70	$156.70
Purchase #5	$223.70	6.385%	$237.9832	$237.98	$238.00	$238.00
Purchase #6	$131.60	5.743%	$139.1578	$139.16	$139.15	$139.20
Purchase #7	$223.82	3.587%	$231.8484	$231.85	$231.85	$231.80
7 purchase totals =	$1,178.24		$1,250.5639	$1,250.56	$1,250.55	$1,250.60