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	$97.91	10.866%	$108.5489	$108.55	$108.55	$108.50
Purchase #2	$223.63	3.681%	$231.8618	$231.86	$231.85	$231.90
Purchase #3	$36.97	9.398%	$40.4444	$40.44	$40.45	$40.40
Purchase #4	$125.39	6.381%	$133.3911	$133.39	$133.40	$133.40
Purchase #5	$60.92	7.103%	$65.2471	$65.25	$65.25	$65.20
Purchase #6	$85.25	13.281%	$96.5721	$96.57	$96.55	$96.60
Purchase #7	$98.86	12.512%	$111.2294	$111.23	$111.25	$111.20
7 purchase totals =	$728.93		$787.2948	$787.29	$787.30	$787.20