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	$79.30	7.843%	$85.5195	$85.52	$85.50	$85.50
Purchase #2	$10.97	12.394%	$12.3296	$12.33	$12.35	$12.30
Purchase #3	$64.40	3.179%	$66.4473	$66.45	$66.45	$66.40
Purchase #4	$137.84	3.517%	$142.6878	$142.69	$142.70	$142.70
Purchase #5	$151.88	11.549%	$169.4206	$169.42	$169.40	$169.40
Purchase #6	$168.59	9.274%	$184.225	$184.23	$184.25	$184.20
Purchase #7	$216.37	12.127%	$242.6092	$242.61	$242.60	$242.60
7 purchase totals =	$829.35		$903.2390	$903.25	$903.25	$903.10