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	10.805%	$187.881	$187.88	$187.90	$187.90
Purchase #2	$140.85	4.796%	$147.6052	$147.61	$147.60	$147.60
Purchase #3	$76.25	3.506%	$78.9233	$78.92	$78.90	$78.90
Purchase #4	$164.53	11.253%	$183.0446	$183.04	$183.05	$183.00
Purchase #5	$219.54	11.792%	$245.4282	$245.43	$245.45	$245.40
Purchase #6	$153.41	13.412%	$173.9853	$173.99	$174.00	$174.00
Purchase #7	$44.63	3.234%	$46.0733	$46.07	$46.05	$46.10
7 purchase totals =	$968.77		$1,062.9409	$1,062.94	$1,062.95	$1,062.90