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	$211.33	5.181%	$222.279	$222.28	$222.30	$222.30
Purchase #2	$60.48	11.665%	$67.535	$67.54	$67.55	$67.50
Purchase #3	$43.60	12.401%	$49.0068	$49.01	$49.00	$49.00
Purchase #4	$185.66	12.734%	$209.3019	$209.30	$209.30	$209.30
Purchase #5	$45.87	4.318%	$47.8507	$47.85	$47.85	$47.90
Purchase #6	$216.60	12.694%	$244.0952	$244.10	$244.10	$244.10
Purchase #7	$148.99	12.134%	$167.0684	$167.07	$167.05	$167.10
7 purchase totals =	$912.53		$1,007.1370	$1,007.15	$1,007.15	$1,007.20