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	$159.92	5.576%	$168.8371	$168.84	$168.85	$168.80
Purchase #2	$208.92	8.250%	$226.1559	$226.16	$226.15	$226.20
Purchase #3	$93.76	8.813%	$102.0231	$102.02	$102.00	$102.00
Purchase #4	$100.33	4.563%	$104.9081	$104.91	$104.90	$104.90
Purchase #5	$204.60	7.263%	$219.4601	$219.46	$219.45	$219.50
Purchase #6	$167.94	13.423%	$190.4826	$190.48	$190.50	$190.50
Purchase #7	$77.29	11.132%	$85.8939	$85.89	$85.90	$85.90
7 purchase totals =	$1,012.76		$1,097.7608	$1,097.76	$1,097.75	$1,097.80