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	$199.76	7.495%	$214.732	$214.73	$214.75	$214.70
Purchase #2	$89.85	6.366%	$95.5699	$95.57	$95.55	$95.60
Purchase #3	$50.73	3.441%	$52.4756	$52.48	$52.50	$52.50
Purchase #4	$246.86	5.771%	$261.1063	$261.11	$261.10	$261.10
Purchase #5	$48.83	11.765%	$54.5748	$54.57	$54.55	$54.60
Purchase #6	$76.64	4.795%	$80.3149	$80.31	$80.30	$80.30
Purchase #7	$86.39	9.370%	$94.4847	$94.48	$94.50	$94.50
7 purchase totals =	$799.06		$853.2582	$853.25	$853.25	$853.30