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	$201.76	11.441%	$224.8434	$224.84	$224.85	$224.80
Purchase #2	$158.59	11.501%	$176.8294	$176.83	$176.85	$176.80
Purchase #3	$47.47	9.565%	$52.0105	$52.01	$52.00	$52.00
Purchase #4	$103.90	7.479%	$111.6707	$111.67	$111.65	$111.70
Purchase #5	$102.54	7.231%	$109.9547	$109.95	$109.95	$110.00
Purchase #6	$18.51	12.688%	$20.8585	$20.86	$20.85	$20.90
Purchase #7	$36.70	3.859%	$38.1163	$38.12	$38.10	$38.10
7 purchase totals =	$669.47		$734.2835	$734.28	$734.25	$734.30