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	$120.57	11.665%	$134.6345	$134.63	$134.65	$134.60
Purchase #2	$163.96	3.273%	$169.3264	$169.33	$169.35	$169.30
Purchase #3	$140.63	11.615%	$156.9642	$156.96	$156.95	$157.00
Purchase #4	$18.74	12.203%	$21.0268	$21.03	$21.05	$21.00
Purchase #5	$96.39	3.131%	$99.408	$99.41	$99.40	$99.40
Purchase #6	$183.85	3.637%	$190.5366	$190.54	$190.55	$190.50
Purchase #7	$50.41	5.600%	$53.233	$53.23	$53.25	$53.20
7 purchase totals =	$774.55		$825.1295	$825.13	$825.20	$825.00