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	$145.50	7.636%	$156.6104	$156.61	$156.60	$156.60
Purchase #2	$221.33	5.732%	$234.0166	$234.02	$234.00	$234.00
Purchase #3	$155.68	3.317%	$160.8439	$160.84	$160.85	$160.80
Purchase #4	$58.28	7.404%	$62.5951	$62.60	$62.60	$62.60
Purchase #5	$197.47	13.257%	$223.6486	$223.65	$223.65	$223.60
Purchase #6	$46.28	10.412%	$51.0987	$51.10	$51.10	$51.10
Purchase #7	$203.91	6.279%	$216.7135	$216.71	$216.70	$216.70
7 purchase totals =	$1,028.45		$1,105.5268	$1,105.53	$1,105.50	$1,105.40