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	$85.28	6.521%	$90.8411	$90.84	$90.85	$90.80
Purchase #2	$21.87	6.522%	$23.2964	$23.30	$23.30	$23.30
Purchase #3	$89.58	11.872%	$100.2149	$100.21	$100.20	$100.20
Purchase #4	$199.86	3.553%	$206.961	$206.96	$206.95	$207.00
Purchase #5	$238.85	7.590%	$256.9787	$256.98	$257.00	$257.00
Purchase #6	$240.47	4.756%	$251.9068	$251.91	$251.90	$251.90
Purchase #7	$79.44	9.445%	$86.9431	$86.94	$86.95	$86.90
7 purchase totals =	$955.35		$1,017.1420	$1,017.14	$1,017.15	$1,017.10