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	$72.28	5.712%	$76.4086	$76.41	$76.40	$76.40
Purchase #2	$199.27	7.821%	$214.8549	$214.85	$214.85	$214.90
Purchase #3	$88.79	13.161%	$100.4757	$100.48	$100.50	$100.50
Purchase #4	$33.33	7.113%	$35.7008	$35.70	$35.70	$35.70
Purchase #5	$104.44	13.628%	$118.6731	$118.67	$118.65	$118.70
Purchase #6	$226.46	11.838%	$253.2683	$253.27	$253.25	$253.30
Purchase #7	$85.66	4.187%	$89.2466	$89.25	$89.25	$89.20
7 purchase totals =	$810.23		$888.6280	$888.63	$888.60	$888.70