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	$102.63	7.417%	$110.2421	$110.24	$110.25	$110.20
Purchase #2	$188.84	4.114%	$196.6089	$196.61	$196.60	$196.60
Purchase #3	$210.70	12.637%	$237.3262	$237.33	$237.35	$237.30
Purchase #4	$95.53	8.622%	$103.7666	$103.77	$103.75	$103.80
Purchase #5	$102.60	5.707%	$108.4554	$108.46	$108.45	$108.50
Purchase #6	$202.65	3.873%	$210.4986	$210.50	$210.50	$210.50
Purchase #7	$46.57	6.320%	$49.5132	$49.51	$49.50	$49.50
7 purchase totals =	$949.52		$1,016.4110	$1,016.42	$1,016.40	$1,016.40