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	$152.46	8.206%	$164.9709	$164.97	$164.95	$165.00
Purchase #2	$145.27	5.277%	$152.9359	$152.94	$152.95	$152.90
Purchase #3	$66.33	13.460%	$75.258	$75.26	$75.25	$75.30
Purchase #4	$242.38	13.819%	$275.8745	$275.87	$275.85	$275.90
Purchase #5	$139.69	3.723%	$144.8907	$144.89	$144.90	$144.90
Purchase #6	$120.71	5.218%	$127.0086	$127.01	$127.00	$127.00
Purchase #7	$92.38	6.212%	$98.1186	$98.12	$98.10	$98.10
7 purchase totals =	$959.22		$1,039.0572	$1,039.06	$1,039.00	$1,039.10