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	$234.86	7.482%	$252.4322	$252.43	$252.45	$252.40
Purchase #2	$84.32	7.262%	$90.4433	$90.44	$90.45	$90.40
Purchase #3	$40.74	10.470%	$45.0055	$45.01	$45.00	$45.00
Purchase #4	$169.75	9.664%	$186.1546	$186.15	$186.15	$186.20
Purchase #5	$145.73	11.377%	$162.3097	$162.31	$162.30	$162.30
Purchase #6	$191.41	6.797%	$204.4201	$204.42	$204.40	$204.40
Purchase #7	$94.65	4.413%	$98.8269	$98.83	$98.85	$98.80
7 purchase totals =	$961.46		$1,039.5923	$1,039.59	$1,039.60	$1,039.50