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	$124.76	4.338%	$130.1721	$130.17	$130.15	$130.20
Purchase #2	$250.58	6.576%	$267.0581	$267.06	$267.05	$267.10
Purchase #3	$139.47	8.113%	$150.7852	$150.79	$150.80	$150.80
Purchase #4	$53.48	11.246%	$59.4944	$59.49	$59.50	$59.50
Purchase #5	$141.80	5.865%	$150.1166	$150.12	$150.10	$150.10
Purchase #6	$224.52	9.729%	$246.3636	$246.36	$246.35	$246.40
Purchase #7	$110.66	11.597%	$123.4932	$123.49	$123.50	$123.50
7 purchase totals =	$1,045.27		$1,127.4832	$1,127.48	$1,127.45	$1,127.60