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	$208.43	6.251%	$221.459	$221.46	$221.45	$221.50
Purchase #2	$246.76	7.434%	$265.1041	$265.10	$265.10	$265.10
Purchase #3	$10.37	9.549%	$11.3602	$11.36	$11.35	$11.40
Purchase #4	$30.69	6.195%	$32.5912	$32.59	$32.60	$32.60
Purchase #5	$128.53	10.752%	$142.3495	$142.35	$142.35	$142.30
Purchase #6	$119.39	9.372%	$130.5792	$130.58	$130.60	$130.60
Purchase #7	$83.34	8.534%	$90.4522	$90.45	$90.45	$90.50
7 purchase totals =	$827.51		$893.8954	$893.89	$893.90	$894.00