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	$157.59	5.578%	$166.3804	$166.38	$166.40	$166.40
Purchase #2	$98.79	10.722%	$109.3823	$109.38	$109.40	$109.40
Purchase #3	$63.98	11.338%	$71.2341	$71.23	$71.25	$71.20
Purchase #4	$121.63	3.445%	$125.8202	$125.82	$125.80	$125.80
Purchase #5	$98.60	8.473%	$106.9544	$106.95	$106.95	$107.00
Purchase #6	$100.99	10.699%	$111.7949	$111.79	$111.80	$111.80
Purchase #7	$143.78	8.238%	$155.6246	$155.62	$155.60	$155.60
7 purchase totals =	$785.36		$847.1909	$847.17	$847.20	$847.20