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	$100.68	11.199%	$111.9552	$111.96	$111.95	$112.00
Purchase #2	$71.62	11.210%	$79.6486	$79.65	$79.65	$79.60
Purchase #3	$125.42	12.701%	$141.3496	$141.35	$141.35	$141.30
Purchase #4	$224.37	5.476%	$236.6565	$236.66	$236.65	$236.70
Purchase #5	$123.45	13.169%	$139.7071	$139.71	$139.70	$139.70
Purchase #6	$116.58	12.629%	$131.3029	$131.30	$131.30	$131.30
Purchase #7	$172.92	3.818%	$179.5221	$179.52	$179.50	$179.50
7 purchase totals =	$935.04		$1,020.1420	$1,020.15	$1,020.10	$1,020.10