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	$145.97	11.536%	$162.8091	$162.81	$162.80	$162.80
Purchase #2	$135.86	11.266%	$151.166	$151.17	$151.15	$151.20
Purchase #3	$160.98	11.861%	$180.0738	$180.07	$180.05	$180.10
Purchase #4	$204.42	11.448%	$227.822	$227.82	$227.80	$227.80
Purchase #5	$88.34	13.641%	$100.3905	$100.39	$100.40	$100.40
Purchase #6	$37.70	11.687%	$42.106	$42.11	$42.10	$42.10
Purchase #7	$237.49	3.219%	$245.1348	$245.13	$245.15	$245.10
7 purchase totals =	$1,010.76		$1,109.5022	$1,109.50	$1,109.45	$1,109.50