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	$217.42	4.626%	$227.4778	$227.48	$227.50	$227.50
Purchase #2	$188.40	12.489%	$211.9293	$211.93	$211.95	$211.90
Purchase #3	$98.90	13.216%	$111.9706	$111.97	$111.95	$112.00
Purchase #4	$197.57	13.368%	$223.9812	$223.98	$224.00	$224.00
Purchase #5	$69.48	11.481%	$77.457	$77.46	$77.45	$77.50
Purchase #6	$5.90	6.779%	$6.3	$6.30	$6.30	$6.30
Purchase #7	$82.27	9.580%	$90.1515	$90.15	$90.15	$90.20
7 purchase totals =	$859.94		$949.2674	$949.27	$949.30	$949.40