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	$150.33	3.330%	$155.336	$155.34	$155.35	$155.30
Purchase #2	$118.34	11.126%	$131.5065	$131.51	$131.50	$131.50
Purchase #3	$64.62	5.120%	$67.9285	$67.93	$67.95	$67.90
Purchase #4	$48.59	6.522%	$51.759	$51.76	$51.75	$51.80
Purchase #5	$30.26	6.771%	$32.3089	$32.31	$32.30	$32.30
Purchase #6	$158.84	8.663%	$172.6003	$172.60	$172.60	$172.60
Purchase #7	$164.53	12.836%	$185.6491	$185.65	$185.65	$185.60
7 purchase totals =	$735.51		$797.0883	$797.10	$797.10	$797.00