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	$115.51	7.115%	$123.7285	$123.73	$123.75	$123.70
Purchase #2	$79.33	10.354%	$87.5438	$87.54	$87.55	$87.50
Purchase #3	$71.66	8.254%	$77.5748	$77.57	$77.55	$77.60
Purchase #4	$191.87	13.661%	$218.0814	$218.08	$218.10	$218.10
Purchase #5	$83.58	7.853%	$90.1435	$90.14	$90.15	$90.10
Purchase #6	$203.46	5.342%	$214.3288	$214.33	$214.35	$214.30
Purchase #7	$205.98	11.633%	$229.9417	$229.94	$229.95	$229.90
7 purchase totals =	$951.39		$1,041.3425	$1,041.33	$1,041.40	$1,041.20