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	$204.64	5.867%	$216.6462	$216.65	$216.65	$216.60
Purchase #2	$131.84	9.402%	$144.2356	$144.24	$144.25	$144.20
Purchase #3	$156.48	5.549%	$165.1631	$165.16	$165.15	$165.20
Purchase #4	$31.63	4.805%	$33.1498	$33.15	$33.15	$33.10
Purchase #5	$136.39	3.774%	$141.5374	$141.54	$141.55	$141.50
Purchase #6	$59.79	11.473%	$66.6497	$66.65	$66.65	$66.60
Purchase #7	$115.43	10.778%	$127.871	$127.87	$127.85	$127.90
7 purchase totals =	$836.20		$895.2528	$895.26	$895.25	$895.10