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	$242.71	9.372%	$265.4568	$265.46	$265.45	$265.50
Purchase #2	$49.94	11.641%	$55.7535	$55.75	$55.75	$55.80
Purchase #3	$184.43	8.506%	$200.1176	$200.12	$200.10	$200.10
Purchase #4	$131.94	9.281%	$144.1854	$144.19	$144.20	$144.20
Purchase #5	$113.51	9.247%	$124.0063	$124.01	$124.00	$124.00
Purchase #6	$55.99	10.419%	$61.8236	$61.82	$61.80	$61.80
Purchase #7	$137.45	10.269%	$151.5647	$151.56	$151.55	$151.60
7 purchase totals =	$915.97		$1,002.9079	$1,002.91	$1,002.85	$1,003.00