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	$170.90	3.190%	$176.3517	$176.35	$176.35	$176.40
Purchase #2	$93.48	3.496%	$96.7481	$96.75	$96.75	$96.70
Purchase #3	$106.34	3.385%	$109.9396	$109.94	$109.95	$109.90
Purchase #4	$166.76	8.502%	$180.9379	$180.94	$180.95	$180.90
Purchase #5	$50.45	8.233%	$54.6035	$54.60	$54.60	$54.60
Purchase #6	$38.96	11.516%	$43.4466	$43.45	$43.45	$43.40
Purchase #7	$222.34	3.434%	$229.9752	$229.98	$230.00	$230.00
7 purchase totals =	$849.23		$892.0026	$892.01	$892.05	$891.90