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	$67.65	4.435%	$70.6503	$70.65	$70.65	$70.70
Purchase #2	$226.76	4.860%	$237.7805	$237.78	$237.80	$237.80
Purchase #3	$168.38	13.607%	$191.2915	$191.29	$191.30	$191.30
Purchase #4	$171.83	4.180%	$179.0125	$179.01	$179.00	$179.00
Purchase #5	$134.45	11.811%	$150.3299	$150.33	$150.35	$150.30
Purchase #6	$213.75	7.321%	$229.3986	$229.40	$229.40	$229.40
Purchase #7	$116.53	13.167%	$131.8735	$131.87	$131.85	$131.90
7 purchase totals =	$1,099.35		$1,190.3368	$1,190.33	$1,190.35	$1,190.40