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	$70.96	12.243%	$79.6476	$79.65	$79.65	$79.60
Purchase #2	$141.99	11.318%	$158.0604	$158.06	$158.05	$158.10
Purchase #3	$87.43	9.714%	$95.923	$95.92	$95.90	$95.90
Purchase #4	$118.74	10.803%	$131.5675	$131.57	$131.55	$131.60
Purchase #5	$96.34	4.190%	$100.3766	$100.38	$100.40	$100.40
Purchase #6	$68.57	6.219%	$72.8344	$72.83	$72.85	$72.80
Purchase #7	$161.80	4.290%	$168.7412	$168.74	$168.75	$168.70
7 purchase totals =	$745.83		$807.1507	$807.15	$807.15	$807.10