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	$31.31	13.182%	$35.4373	$35.44	$35.45	$35.40
Purchase #2	$157.28	9.839%	$172.7548	$172.75	$172.75	$172.80
Purchase #3	$101.52	10.315%	$111.9918	$111.99	$112.00	$112.00
Purchase #4	$208.97	12.125%	$234.3076	$234.31	$234.30	$234.30
Purchase #5	$155.41	12.326%	$174.5658	$174.57	$174.55	$174.60
Purchase #6	$222.56	12.750%	$250.9364	$250.94	$250.95	$250.90
Purchase #7	$139.38	12.322%	$156.5544	$156.55	$156.55	$156.60
7 purchase totals =	$1,016.43		$1,136.5481	$1,136.55	$1,136.55	$1,136.60