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	$112.82	10.779%	$124.9809	$124.98	$125.00	$125.00
Purchase #2	$165.29	8.650%	$179.5876	$179.59	$179.60	$179.60
Purchase #3	$240.43	10.870%	$266.5647	$266.56	$266.55	$266.60
Purchase #4	$145.39	12.608%	$163.7208	$163.72	$163.70	$163.70
Purchase #5	$39.60	6.516%	$42.1803	$42.18	$42.20	$42.20
Purchase #6	$202.43	7.766%	$218.1507	$218.15	$218.15	$218.20
Purchase #7	$65.54	10.784%	$72.6078	$72.61	$72.60	$72.60
7 purchase totals =	$971.50		$1,067.7928	$1,067.79	$1,067.80	$1,067.90