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	$95.34	10.371%	$105.2277	$105.23	$105.25	$105.20
Purchase #2	$123.95	11.275%	$137.9254	$137.93	$137.95	$137.90
Purchase #3	$248.31	5.585%	$262.1781	$262.18	$262.20	$262.20
Purchase #4	$49.54	10.676%	$54.8289	$54.83	$54.85	$54.80
Purchase #5	$237.70	12.280%	$266.8896	$266.89	$266.90	$266.90
Purchase #6	$229.49	3.165%	$236.7534	$236.75	$236.75	$236.80
Purchase #7	$56.77	7.520%	$61.0391	$61.04	$61.05	$61.00
7 purchase totals =	$1,041.10		$1,124.8422	$1,124.85	$1,124.95	$1,124.80