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	$103.78	7.803%	$111.878	$111.88	$111.90	$111.90
Purchase #2	$175.52	13.593%	$199.3784	$199.38	$199.40	$199.40
Purchase #3	$80.88	5.306%	$85.1715	$85.17	$85.15	$85.20
Purchase #4	$203.66	9.277%	$222.5535	$222.55	$222.55	$222.60
Purchase #5	$49.59	9.423%	$54.2629	$54.26	$54.25	$54.30
Purchase #6	$201.89	11.161%	$224.4229	$224.42	$224.40	$224.40
Purchase #7	$214.33	3.380%	$221.5744	$221.57	$221.55	$221.60
7 purchase totals =	$1,029.65		$1,119.2416	$1,119.23	$1,119.20	$1,119.40