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	$144.31	7.680%	$155.393	$155.39	$155.40	$155.40
Purchase #2	$71.75	9.694%	$78.7054	$78.71	$78.70	$78.70
Purchase #3	$205.94	13.304%	$233.3383	$233.34	$233.35	$233.30
Purchase #4	$61.95	8.321%	$67.1049	$67.10	$67.10	$67.10
Purchase #5	$177.65	11.612%	$198.2787	$198.28	$198.30	$198.30
Purchase #6	$5.50	6.569%	$5.8613	$5.86	$5.85	$5.90
Purchase #7	$36.33	9.778%	$39.8823	$39.88	$39.90	$39.90
7 purchase totals =	$703.43		$778.5639	$778.56	$778.60	$778.60