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	$233.46	13.472%	$264.9117	$264.91	$264.90	$264.90
Purchase #2	$31.77	4.581%	$33.2254	$33.23	$33.25	$33.20
Purchase #3	$156.36	11.750%	$174.7323	$174.73	$174.75	$174.70
Purchase #4	$70.68	10.772%	$78.2936	$78.29	$78.30	$78.30
Purchase #5	$141.80	13.552%	$161.0167	$161.02	$161.00	$161.00
Purchase #6	$245.90	3.124%	$253.5819	$253.58	$253.60	$253.60
Purchase #7	$143.58	9.588%	$157.3465	$157.35	$157.35	$157.30
7 purchase totals =	$1,023.55		$1,123.1081	$1,123.11	$1,123.15	$1,123.00