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	$28.40	3.434%	$29.3753	$29.38	$29.40	$29.40
Purchase #2	$102.96	8.160%	$111.3615	$111.36	$111.35	$111.40
Purchase #3	$246.82	8.319%	$267.353	$267.35	$267.35	$267.40
Purchase #4	$153.65	11.303%	$171.0171	$171.02	$171.00	$171.00
Purchase #5	$234.52	11.453%	$261.3796	$261.38	$261.40	$261.40
Purchase #6	$103.62	7.352%	$111.2381	$111.24	$111.25	$111.20
Purchase #7	$88.51	8.170%	$95.7413	$95.74	$95.75	$95.70
7 purchase totals =	$958.48		$1,047.4659	$1,047.47	$1,047.50	$1,047.50