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	$156.73	10.862%	$173.754	$173.75	$173.75	$173.80
Purchase #2	$138.45	9.652%	$151.8132	$151.81	$151.80	$151.80
Purchase #3	$92.54	12.642%	$104.2389	$104.24	$104.25	$104.20
Purchase #4	$94.65	12.616%	$106.591	$106.59	$106.60	$106.60
Purchase #5	$89.91	11.108%	$99.8972	$99.90	$99.90	$99.90
Purchase #6	$24.44	4.387%	$25.5122	$25.51	$25.50	$25.50
Purchase #7	$170.91	8.820%	$185.9843	$185.98	$186.00	$186.00
7 purchase totals =	$767.63		$847.7908	$847.78	$847.80	$847.80