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	$183.33	8.470%	$198.8581	$198.86	$198.85	$198.90
Purchase #2	$141.81	10.821%	$157.1553	$157.16	$157.15	$157.20
Purchase #3	$230.54	11.210%	$256.3835	$256.38	$256.40	$256.40
Purchase #4	$126.35	13.456%	$143.3517	$143.35	$143.35	$143.40
Purchase #5	$104.68	5.425%	$110.3589	$110.36	$110.35	$110.40
Purchase #6	$36.31	4.153%	$37.818	$37.82	$37.80	$37.80
Purchase #7	$19.26	13.637%	$21.8865	$21.89	$21.90	$21.90
7 purchase totals =	$842.28		$925.8120	$925.82	$925.80	$926.00