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	$103.53	5.417%	$109.1382	$109.14	$109.15	$109.10
Purchase #2	$131.61	7.430%	$141.3886	$141.39	$141.40	$141.40
Purchase #3	$205.30	12.841%	$231.6626	$231.66	$231.65	$231.70
Purchase #4	$87.88	7.620%	$94.5765	$94.58	$94.60	$94.60
Purchase #5	$191.90	13.440%	$217.6914	$217.69	$217.70	$217.70
Purchase #6	$235.77	11.360%	$262.5535	$262.55	$262.55	$262.60
Purchase #7	$37.34	5.414%	$39.3616	$39.36	$39.35	$39.40
7 purchase totals =	$993.33		$1,096.3724	$1,096.37	$1,096.40	$1,096.50