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	$108.26	3.418%	$111.9603	$111.96	$111.95	$112.00
Purchase #2	$240.35	3.539%	$248.856	$248.86	$248.85	$248.90
Purchase #3	$5.41	10.545%	$5.9805	$5.98	$6.00	$6.00
Purchase #4	$39.33	4.325%	$41.031	$41.03	$41.05	$41.00
Purchase #5	$53.77	9.847%	$59.0647	$59.06	$59.05	$59.10
Purchase #6	$161.54	4.667%	$169.0791	$169.08	$169.10	$169.10
Purchase #7	$111.58	5.618%	$117.8486	$117.85	$117.85	$117.80
7 purchase totals =	$720.24		$753.8202	$753.82	$753.85	$753.90