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	$165.93	5.595%	$175.2138	$175.21	$175.20	$175.20
Purchase #2	$78.31	5.404%	$82.5419	$82.54	$82.55	$82.50
Purchase #3	$173.63	4.189%	$180.9034	$180.90	$180.90	$180.90
Purchase #4	$116.87	3.182%	$120.5888	$120.59	$120.60	$120.60
Purchase #5	$172.96	12.594%	$194.7426	$194.74	$194.75	$194.70
Purchase #6	$36.71	11.199%	$40.8212	$40.82	$40.80	$40.80
Purchase #7	$247.71	7.595%	$266.5236	$266.52	$266.50	$266.50
7 purchase totals =	$992.12		$1,061.3353	$1,061.32	$1,061.30	$1,061.20