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	$38.91	10.789%	$43.108	$43.11	$43.10	$43.10
Purchase #2	$22.61	4.127%	$23.5431	$23.54	$23.55	$23.50
Purchase #3	$221.41	9.820%	$243.1525	$243.15	$243.15	$243.20
Purchase #4	$111.37	11.281%	$123.9336	$123.93	$123.95	$123.90
Purchase #5	$229.76	3.763%	$238.4059	$238.41	$238.40	$238.40
Purchase #6	$21.92	11.397%	$24.4182	$24.42	$24.40	$24.40
Purchase #7	$34.46	7.401%	$37.0104	$37.01	$37.00	$37.00
7 purchase totals =	$680.44		$733.5717	$733.57	$733.55	$733.50