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	$60.77	11.594%	$67.8157	$67.82	$67.80	$67.80
Purchase #2	$159.95	4.380%	$166.9558	$166.96	$166.95	$167.00
Purchase #3	$27.87	9.656%	$30.5611	$30.56	$30.55	$30.60
Purchase #4	$6.60	12.541%	$7.4277	$7.43	$7.45	$7.40
Purchase #5	$113.36	12.606%	$127.6502	$127.65	$127.65	$127.70
Purchase #6	$87.44	13.820%	$99.5242	$99.52	$99.50	$99.50
Purchase #7	$25.46	8.505%	$27.6254	$27.63	$27.65	$27.60
7 purchase totals =	$481.45		$527.5601	$527.57	$527.55	$527.60