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	$184.49	6.506%	$196.4929	$196.49	$196.50	$196.50
Purchase #2	$140.81	13.144%	$159.3181	$159.32	$159.30	$159.30
Purchase #3	$184.62	13.410%	$209.3775	$209.38	$209.40	$209.40
Purchase #4	$75.63	3.202%	$78.0517	$78.05	$78.05	$78.10
Purchase #5	$23.59	8.162%	$25.5154	$25.52	$25.50	$25.50
Purchase #6	$197.36	12.406%	$221.8445	$221.84	$221.85	$221.80
Purchase #7	$68.59	5.439%	$72.3206	$72.32	$72.30	$72.30
7 purchase totals =	$875.09		$962.9207	$962.92	$962.90	$962.90