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	$228.97	7.413%	$245.9435	$245.94	$245.95	$245.90
Purchase #2	$163.74	6.559%	$174.4797	$174.48	$174.50	$174.50
Purchase #3	$54.36	9.132%	$59.3242	$59.32	$59.30	$59.30
Purchase #4	$147.87	11.612%	$165.0407	$165.04	$165.05	$165.00
Purchase #5	$139.37	3.594%	$144.379	$144.38	$144.40	$144.40
Purchase #6	$116.62	13.387%	$132.2319	$132.23	$132.25	$132.20
Purchase #7	$49.84	6.813%	$53.2356	$53.24	$53.25	$53.20
7 purchase totals =	$900.77		$974.6346	$974.63	$974.70	$974.50