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	$169.56	8.437%	$183.8658	$183.87	$183.85	$183.90
Purchase #2	$127.73	13.762%	$145.3082	$145.31	$145.30	$145.30
Purchase #3	$224.36	6.493%	$238.9277	$238.93	$238.95	$238.90
Purchase #4	$73.55	11.628%	$82.1024	$82.10	$82.10	$82.10
Purchase #5	$150.61	12.401%	$169.2871	$169.29	$169.30	$169.30
Purchase #6	$85.29	4.478%	$89.1093	$89.11	$89.10	$89.10
Purchase #7	$169.82	3.404%	$175.6007	$175.60	$175.60	$175.60
7 purchase totals =	$1,000.92		$1,084.2012	$1,084.21	$1,084.20	$1,084.20