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	$172.46	5.206%	$181.4383	$181.44	$181.45	$181.40
Purchase #2	$162.28	9.622%	$177.8946	$177.89	$177.90	$177.90
Purchase #3	$10.89	11.524%	$12.145	$12.15	$12.15	$12.10
Purchase #4	$102.31	4.723%	$107.1421	$107.14	$107.15	$107.10
Purchase #5	$55.81	6.855%	$59.6358	$59.64	$59.65	$59.60
Purchase #6	$145.97	13.249%	$165.3096	$165.31	$165.30	$165.30
Purchase #7	$100.89	8.288%	$109.2518	$109.25	$109.25	$109.30
7 purchase totals =	$750.61		$812.8172	$812.82	$812.85	$812.70