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	$174.63	4.872%	$183.138	$183.14	$183.15	$183.10
Purchase #2	$116.34	6.530%	$123.937	$123.94	$123.95	$123.90
Purchase #3	$250.33	11.528%	$279.188	$279.19	$279.20	$279.20
Purchase #4	$184.37	3.512%	$190.8451	$190.85	$190.85	$190.80
Purchase #5	$17.41	7.564%	$18.7269	$18.73	$18.75	$18.70
Purchase #6	$9.59	12.816%	$10.8191	$10.82	$10.80	$10.80
Purchase #7	$231.26	6.164%	$245.5149	$245.51	$245.50	$245.50
7 purchase totals =	$983.93		$1,052.1690	$1,052.18	$1,052.20	$1,052.00