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	$131.77	12.132%	$147.7563	$147.76	$147.75	$147.80
Purchase #2	$108.99	7.651%	$117.3288	$117.33	$117.35	$117.30
Purchase #3	$196.81	6.422%	$209.4491	$209.45	$209.45	$209.40
Purchase #4	$37.47	13.432%	$42.503	$42.50	$42.50	$42.50
Purchase #5	$191.54	6.189%	$203.3944	$203.39	$203.40	$203.40
Purchase #6	$54.49	12.670%	$61.3939	$61.39	$61.40	$61.40
Purchase #7	$75.28	4.209%	$78.4485	$78.45	$78.45	$78.40
7 purchase totals =	$796.35		$860.2740	$860.27	$860.30	$860.20