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	$184.72	8.191%	$199.8504	$199.85	$199.85	$199.90
Purchase #2	$22.25	13.737%	$25.3065	$25.31	$25.30	$25.30
Purchase #3	$139.73	9.229%	$152.6257	$152.63	$152.65	$152.60
Purchase #4	$209.32	3.854%	$217.3872	$217.39	$217.40	$217.40
Purchase #5	$30.74	4.431%	$32.1021	$32.10	$32.10	$32.10
Purchase #6	$233.92	3.782%	$242.7669	$242.77	$242.75	$242.80
Purchase #7	$34.96	9.862%	$38.4078	$38.41	$38.40	$38.40
7 purchase totals =	$855.64		$908.4466	$908.46	$908.45	$908.50