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	$153.85	6.748%	$164.2318	$164.23	$164.25	$164.20
Purchase #2	$102.88	10.585%	$113.7698	$113.77	$113.75	$113.80
Purchase #3	$183.53	7.248%	$196.8323	$196.83	$196.85	$196.80
Purchase #4	$98.39	6.221%	$104.5108	$104.51	$104.50	$104.50
Purchase #5	$103.71	6.389%	$110.336	$110.34	$110.35	$110.30
Purchase #6	$238.53	8.296%	$258.3184	$258.32	$258.30	$258.30
Purchase #7	$209.99	6.468%	$223.5722	$223.57	$223.55	$223.60
7 purchase totals =	$1,090.88		$1,171.5713	$1,171.57	$1,171.55	$1,171.50