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	$65.37	7.548%	$70.3041	$70.30	$70.30	$70.30
Purchase #2	$41.33	10.131%	$45.5171	$45.52	$45.50	$45.50
Purchase #3	$42.75	8.763%	$46.4962	$46.50	$46.50	$46.50
Purchase #4	$10.50	11.296%	$11.6861	$11.69	$11.70	$11.70
Purchase #5	$236.80	13.626%	$269.0664	$269.07	$269.05	$269.10
Purchase #6	$163.91	4.423%	$171.1597	$171.16	$171.15	$171.20
Purchase #7	$51.27	11.595%	$57.2148	$57.21	$57.20	$57.20
7 purchase totals =	$611.93		$671.4444	$671.45	$671.40	$671.50