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	$93.60	10.870%	$103.7743	$103.77	$103.75	$103.80
Purchase #2	$164.71	3.530%	$170.5243	$170.52	$170.50	$170.50
Purchase #3	$229.33	7.197%	$245.8349	$245.83	$245.85	$245.80
Purchase #4	$197.33	13.401%	$223.7742	$223.77	$223.75	$223.80
Purchase #5	$60.95	3.800%	$63.2661	$63.27	$63.25	$63.30
Purchase #6	$37.74	11.336%	$42.0182	$42.02	$42.00	$42.00
Purchase #7	$161.64	5.518%	$170.5593	$170.56	$170.55	$170.60
7 purchase totals =	$945.30		$1,019.7513	$1,019.74	$1,019.65	$1,019.80