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	$100.54	4.575%	$105.1397	$105.14	$105.15	$105.10
Purchase #2	$71.81	13.658%	$81.6178	$81.62	$81.60	$81.60
Purchase #3	$34.33	10.132%	$37.8083	$37.81	$37.80	$37.80
Purchase #4	$222.63	11.586%	$248.4239	$248.42	$248.40	$248.40
Purchase #5	$169.63	12.159%	$190.2553	$190.26	$190.25	$190.30
Purchase #6	$49.80	11.297%	$55.4259	$55.43	$55.45	$55.40
Purchase #7	$178.48	7.437%	$191.7536	$191.75	$191.75	$191.80
7 purchase totals =	$827.22		$910.4245	$910.43	$910.40	$910.40