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	$227.66	4.171%	$237.1557	$237.16	$237.15	$237.20
Purchase #2	$95.84	8.412%	$103.9021	$103.90	$103.90	$103.90
Purchase #3	$151.39	4.666%	$158.4539	$158.45	$158.45	$158.50
Purchase #4	$92.77	6.609%	$98.9012	$98.90	$98.90	$98.90
Purchase #5	$14.33	11.794%	$16.0201	$16.02	$16.00	$16.00
Purchase #6	$122.46	7.674%	$131.8576	$131.86	$131.85	$131.90
Purchase #7	$40.66	13.709%	$46.2341	$46.23	$46.25	$46.20
7 purchase totals =	$745.11		$792.5247	$792.52	$792.50	$792.60