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	$86.69	10.269%	$95.5922	$95.59	$95.60	$95.60
Purchase #2	$211.75	10.266%	$233.4883	$233.49	$233.50	$233.50
Purchase #3	$88.82	11.494%	$99.029	$99.03	$99.05	$99.00
Purchase #4	$107.44	5.284%	$113.1171	$113.12	$113.10	$113.10
Purchase #5	$39.71	11.477%	$44.2675	$44.27	$44.25	$44.30
Purchase #6	$180.51	9.390%	$197.4599	$197.46	$197.45	$197.50
Purchase #7	$100.38	13.845%	$114.2776	$114.28	$114.30	$114.30
7 purchase totals =	$815.30		$897.2316	$897.24	$897.25	$897.30