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	$196.45	11.789%	$219.6095	$219.61	$219.60	$219.60
Purchase #2	$245.38	12.140%	$275.1691	$275.17	$275.15	$275.20
Purchase #3	$214.34	4.461%	$223.9017	$223.90	$223.90	$223.90
Purchase #4	$119.33	3.773%	$123.8323	$123.83	$123.85	$123.80
Purchase #5	$141.66	4.326%	$147.7882	$147.79	$147.80	$147.80
Purchase #6	$9.69	11.529%	$10.8072	$10.81	$10.80	$10.80
Purchase #7	$127.46	11.296%	$141.8579	$141.86	$141.85	$141.90
7 purchase totals =	$1,054.31		$1,142.9659	$1,142.97	$1,142.95	$1,143.00