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	$43.93	3.530%	$45.4807	$45.48	$45.50	$45.50
Purchase #2	$129.31	6.270%	$137.4177	$137.42	$137.40	$137.40
Purchase #3	$92.40	4.242%	$96.3196	$96.32	$96.30	$96.30
Purchase #4	$76.70	8.785%	$83.4381	$83.44	$83.45	$83.40
Purchase #5	$167.70	4.628%	$175.4612	$175.46	$175.45	$175.50
Purchase #6	$146.97	4.197%	$153.1383	$153.14	$153.15	$153.10
Purchase #7	$233.39	7.549%	$251.0086	$251.01	$251.00	$251.00
7 purchase totals =	$890.40		$942.2642	$942.27	$942.25	$942.20