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	$88.43	11.123%	$98.2661	$98.27	$98.25	$98.30
Purchase #2	$87.37	9.322%	$95.5146	$95.51	$95.50	$95.50
Purchase #3	$173.30	11.825%	$193.7927	$193.79	$193.80	$193.80
Purchase #4	$39.46	12.782%	$44.5038	$44.50	$44.50	$44.50
Purchase #5	$55.60	6.850%	$59.4086	$59.41	$59.40	$59.40
Purchase #6	$50.99	12.685%	$57.4581	$57.46	$57.45	$57.50
Purchase #7	$162.72	3.801%	$168.905	$168.91	$168.90	$168.90
7 purchase totals =	$657.87		$717.8489	$717.85	$717.80	$717.90