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	$250.39	12.613%	$281.9717	$281.97	$281.95	$282.00
Purchase #2	$145.29	4.310%	$151.552	$151.55	$151.55	$151.60
Purchase #3	$182.93	9.640%	$200.5645	$200.56	$200.55	$200.60
Purchase #4	$99.36	7.106%	$106.4205	$106.42	$106.40	$106.40
Purchase #5	$57.32	7.737%	$61.7548	$61.75	$61.75	$61.80
Purchase #6	$80.84	11.170%	$89.8698	$89.87	$89.85	$89.90
Purchase #7	$137.59	8.838%	$149.7502	$149.75	$149.75	$149.80
7 purchase totals =	$953.72		$1,041.8835	$1,041.87	$1,041.80	$1,042.10