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	$141.32	6.669%	$150.7446	$150.74	$150.75	$150.70
Purchase #2	$16.91	9.114%	$18.4512	$18.45	$18.45	$18.50
Purchase #3	$16.76	13.705%	$19.057	$19.06	$19.05	$19.10
Purchase #4	$148.62	13.382%	$168.5083	$168.51	$168.50	$168.50
Purchase #5	$107.47	6.130%	$114.0579	$114.06	$114.05	$114.10
Purchase #6	$147.39	13.256%	$166.928	$166.93	$166.95	$166.90
Purchase #7	$156.73	6.853%	$167.4707	$167.47	$167.45	$167.50
7 purchase totals =	$735.20		$805.2177	$805.22	$805.20	$805.30