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	$196.30	12.137%	$220.1249	$220.12	$220.10	$220.10
Purchase #2	$171.56	7.786%	$184.9177	$184.92	$184.90	$184.90
Purchase #3	$160.66	9.322%	$175.6367	$175.64	$175.65	$175.60
Purchase #4	$33.73	8.690%	$36.6611	$36.66	$36.65	$36.70
Purchase #5	$134.64	8.134%	$145.5916	$145.59	$145.60	$145.60
Purchase #6	$31.50	9.593%	$34.5218	$34.52	$34.50	$34.50
Purchase #7	$199.32	11.579%	$222.3993	$222.40	$222.40	$222.40
7 purchase totals =	$927.71		$1,019.8531	$1,019.85	$1,019.80	$1,019.80