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	$173.59	10.520%	$191.8517	$191.85	$191.85	$191.90
Purchase #2	$52.78	5.384%	$55.6217	$55.62	$55.60	$55.60
Purchase #3	$220.45	12.111%	$247.1487	$247.15	$247.15	$247.10
Purchase #4	$185.33	12.248%	$208.0292	$208.03	$208.05	$208.00
Purchase #5	$143.53	10.450%	$158.5289	$158.53	$158.55	$158.50
Purchase #6	$127.54	4.422%	$133.1798	$133.18	$133.20	$133.20
Purchase #7	$155.44	12.409%	$174.7285	$174.73	$174.75	$174.70
7 purchase totals =	$1,058.66		$1,169.0885	$1,169.09	$1,169.15	$1,169.00