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	$49.38	8.408%	$53.5319	$53.53	$53.55	$53.50
Purchase #2	$76.48	5.501%	$80.6872	$80.69	$80.70	$80.70
Purchase #3	$183.57	6.557%	$195.6067	$195.61	$195.60	$195.60
Purchase #4	$112.65	12.464%	$126.6907	$126.69	$126.70	$126.70
Purchase #5	$37.48	8.351%	$40.61	$40.61	$40.60	$40.60
Purchase #6	$224.45	12.236%	$251.9137	$251.91	$251.90	$251.90
Purchase #7	$224.84	13.589%	$255.3935	$255.39	$255.40	$255.40
7 purchase totals =	$908.85		$1,004.4337	$1,004.43	$1,004.45	$1,004.40