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	$188.85	4.287%	$196.946	$196.95	$196.95	$196.90
Purchase #2	$37.66	13.169%	$42.6194	$42.62	$42.60	$42.60
Purchase #3	$58.59	5.609%	$61.8763	$61.88	$61.90	$61.90
Purchase #4	$185.93	13.139%	$210.3593	$210.36	$210.35	$210.40
Purchase #5	$141.73	12.782%	$159.8459	$159.85	$159.85	$159.80
Purchase #6	$179.41	5.844%	$189.8947	$189.89	$189.90	$189.90
Purchase #7	$160.32	10.743%	$177.5432	$177.54	$177.55	$177.50
7 purchase totals =	$952.49		$1,039.0848	$1,039.09	$1,039.10	$1,039.00