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	$104.44	6.318%	$111.0385	$111.04	$111.05	$111.00
Purchase #2	$184.78	7.188%	$198.062	$198.06	$198.05	$198.10
Purchase #3	$27.45	10.132%	$30.2312	$30.23	$30.25	$30.20
Purchase #4	$166.49	8.682%	$180.9447	$180.94	$180.95	$180.90
Purchase #5	$84.73	6.331%	$90.0943	$90.09	$90.10	$90.10
Purchase #6	$30.38	5.114%	$31.9336	$31.93	$31.95	$31.90
Purchase #7	$72.90	7.380%	$78.28	$78.28	$78.30	$78.30
7 purchase totals =	$671.17		$720.5843	$720.57	$720.65	$720.50