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	$135.53	7.431%	$145.6012	$145.60	$145.60	$145.60
Purchase #2	$46.89	9.431%	$51.3122	$51.31	$51.30	$51.30
Purchase #3	$201.65	4.790%	$211.309	$211.31	$211.30	$211.30
Purchase #4	$238.52	9.380%	$260.8932	$260.89	$260.90	$260.90
Purchase #5	$179.59	5.650%	$189.7368	$189.74	$189.75	$189.70
Purchase #6	$222.40	12.796%	$250.8583	$250.86	$250.85	$250.90
Purchase #7	$38.35	3.233%	$39.5899	$39.59	$39.60	$39.60
7 purchase totals =	$1,062.93		$1,149.3006	$1,149.30	$1,149.30	$1,149.30