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	$88.69	7.499%	$95.3409	$95.34	$95.35	$95.30
Purchase #2	$109.37	3.562%	$113.2658	$113.27	$113.25	$113.30
Purchase #3	$187.66	11.759%	$209.7269	$209.73	$209.75	$209.70
Purchase #4	$61.60	5.624%	$65.0644	$65.06	$65.05	$65.10
Purchase #5	$52.43	3.573%	$54.3033	$54.30	$54.30	$54.30
Purchase #6	$40.38	6.142%	$42.8601	$42.86	$42.85	$42.90
Purchase #7	$177.28	6.556%	$188.9025	$188.90	$188.90	$188.90
7 purchase totals =	$717.41		$769.4639	$769.46	$769.45	$769.50