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	$142.76	9.196%	$155.8882	$155.89	$155.90	$155.90
Purchase #2	$40.72	12.714%	$45.8971	$45.90	$45.90	$45.90
Purchase #3	$26.81	4.577%	$28.0371	$28.04	$28.05	$28.00
Purchase #4	$89.93	13.279%	$101.8718	$101.87	$101.85	$101.90
Purchase #5	$59.96	12.651%	$67.5455	$67.55	$67.55	$67.50
Purchase #6	$130.43	13.860%	$148.5076	$148.51	$148.50	$148.50
Purchase #7	$146.28	13.177%	$165.5553	$165.56	$165.55	$165.60
7 purchase totals =	$636.89		$713.3026	$713.32	$713.30	$713.30