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	$249.98	10.214%	$275.513	$275.51	$275.50	$275.50
Purchase #2	$119.26	4.565%	$124.7042	$124.70	$124.70	$124.70
Purchase #3	$182.52	7.128%	$195.53	$195.53	$195.55	$195.50
Purchase #4	$54.95	9.625%	$60.2389	$60.24	$60.25	$60.20
Purchase #5	$202.71	13.359%	$229.79	$229.79	$229.80	$229.80
Purchase #6	$91.89	8.489%	$99.6905	$99.69	$99.70	$99.70
Purchase #7	$27.42	13.358%	$31.0828	$31.08	$31.10	$31.10
7 purchase totals =	$928.73		$1,016.5494	$1,016.54	$1,016.60	$1,016.50