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	$182.65	6.290%	$194.1387	$194.14	$194.15	$194.10
Purchase #2	$42.57	7.808%	$45.8939	$45.89	$45.90	$45.90
Purchase #3	$199.90	9.308%	$218.5067	$218.51	$218.50	$218.50
Purchase #4	$70.66	4.321%	$73.7132	$73.71	$73.70	$73.70
Purchase #5	$141.78	9.232%	$154.8691	$154.87	$154.85	$154.90
Purchase #6	$41.56	10.421%	$45.891	$45.89	$45.90	$45.90
Purchase #7	$66.84	3.837%	$69.4047	$69.40	$69.40	$69.40
7 purchase totals =	$745.96		$802.4173	$802.41	$802.40	$802.40