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	$85.44	6.811%	$91.2593	$91.26	$91.25	$91.30
Purchase #2	$39.80	7.765%	$42.8905	$42.89	$42.90	$42.90
Purchase #3	$7.34	7.552%	$7.8943	$7.89	$7.90	$7.90
Purchase #4	$67.46	4.513%	$70.5045	$70.50	$70.50	$70.50
Purchase #5	$106.97	6.441%	$113.8599	$113.86	$113.85	$113.90
Purchase #6	$239.71	9.834%	$263.2831	$263.28	$263.30	$263.30
Purchase #7	$19.38	8.508%	$21.0289	$21.03	$21.05	$21.00
7 purchase totals =	$566.10		$610.7205	$610.71	$610.75	$610.80