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	$236.81	4.735%	$248.023	$248.02	$248.00	$248.00
Purchase #2	$36.91	9.530%	$40.4275	$40.43	$40.45	$40.40
Purchase #3	$92.54	4.692%	$96.882	$96.88	$96.90	$96.90
Purchase #4	$43.46	9.538%	$47.6052	$47.61	$47.60	$47.60
Purchase #5	$206.86	11.104%	$229.8297	$229.83	$229.85	$229.80
Purchase #6	$212.88	3.360%	$220.0328	$220.03	$220.05	$220.00
Purchase #7	$38.67	9.581%	$42.375	$42.38	$42.40	$42.40
7 purchase totals =	$868.13		$925.1752	$925.18	$925.25	$925.10