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	$191.80	4.309%	$200.0647	$200.06	$200.05	$200.10
Purchase #2	$242.78	12.657%	$273.5087	$273.51	$273.50	$273.50
Purchase #3	$225.57	8.841%	$245.5126	$245.51	$245.50	$245.50
Purchase #4	$27.49	8.803%	$29.9099	$29.91	$29.90	$29.90
Purchase #5	$69.46	7.820%	$74.8918	$74.89	$74.90	$74.90
Purchase #6	$209.63	3.385%	$216.726	$216.73	$216.75	$216.70
Purchase #7	$184.84	6.184%	$196.2705	$196.27	$196.25	$196.30
7 purchase totals =	$1,151.57		$1,236.8842	$1,236.88	$1,236.85	$1,236.90