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	$228.60	6.839%	$244.234	$244.23	$244.25	$244.20
Purchase #2	$130.87	12.243%	$146.8924	$146.89	$146.90	$146.90
Purchase #3	$42.91	12.793%	$48.3995	$48.40	$48.40	$48.40
Purchase #4	$54.51	9.201%	$59.5255	$59.53	$59.55	$59.50
Purchase #5	$142.65	12.593%	$160.6139	$160.61	$160.60	$160.60
Purchase #6	$196.83	4.326%	$205.3449	$205.34	$205.35	$205.30
Purchase #7	$150.30	4.331%	$156.8095	$156.81	$156.80	$156.80
7 purchase totals =	$946.67		$1,021.8197	$1,021.81	$1,021.85	$1,021.70