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	$95.41	5.836%	$100.9781	$100.98	$101.00	$101.00
Purchase #2	$191.92	4.330%	$200.2301	$200.23	$200.25	$200.20
Purchase #3	$88.67	13.343%	$100.5012	$100.50	$100.50	$100.50
Purchase #4	$193.55	7.629%	$208.3159	$208.32	$208.30	$208.30
Purchase #5	$184.51	8.220%	$199.6767	$199.68	$199.70	$199.70
Purchase #6	$164.94	5.757%	$174.4356	$174.44	$174.45	$174.40
Purchase #7	$107.64	4.431%	$112.4095	$112.41	$112.40	$112.40
7 purchase totals =	$1,026.64		$1,096.5471	$1,096.56	$1,096.60	$1,096.50