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	$117.45	8.756%	$127.7339	$127.73	$127.75	$127.70
Purchase #2	$199.69	8.543%	$216.7495	$216.75	$216.75	$216.70
Purchase #3	$86.71	3.118%	$89.4136	$89.41	$89.40	$89.40
Purchase #4	$20.28	5.852%	$21.4668	$21.47	$21.45	$21.50
Purchase #5	$95.45	5.678%	$100.8697	$100.87	$100.85	$100.90
Purchase #6	$231.47	10.213%	$255.11	$255.11	$255.10	$255.10
Purchase #7	$78.91	4.122%	$82.1627	$82.16	$82.15	$82.20
7 purchase totals =	$829.96		$893.5062	$893.50	$893.45	$893.50