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	$173.27	5.251%	$182.3684	$182.37	$182.35	$182.40
Purchase #2	$171.90	4.403%	$179.4688	$179.47	$179.45	$179.50
Purchase #3	$123.99	5.567%	$130.8925	$130.89	$130.90	$130.90
Purchase #4	$30.70	6.265%	$32.6234	$32.62	$32.60	$32.60
Purchase #5	$77.54	5.552%	$81.845	$81.85	$81.85	$81.80
Purchase #6	$36.37	12.396%	$40.8784	$40.88	$40.90	$40.90
Purchase #7	$129.76	13.857%	$147.7408	$147.74	$147.75	$147.70
7 purchase totals =	$743.53		$795.8173	$795.82	$795.80	$795.80