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	$97.92	7.237%	$105.0065	$105.01	$105.00	$105.00
Purchase #2	$103.86	3.539%	$107.5356	$107.54	$107.55	$107.50
Purchase #3	$40.73	11.636%	$45.4693	$45.47	$45.45	$45.50
Purchase #4	$28.90	12.410%	$32.4865	$32.49	$32.50	$32.50
Purchase #5	$37.84	4.834%	$39.6692	$39.67	$39.65	$39.70
Purchase #6	$188.73	5.231%	$198.6025	$198.60	$198.60	$198.60
Purchase #7	$235.41	9.713%	$258.2754	$258.28	$258.30	$258.30
7 purchase totals =	$733.39		$787.0450	$787.06	$787.05	$787.10