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	$250.90	7.544%	$269.8279	$269.83	$269.85	$269.80
Purchase #2	$219.98	10.744%	$243.6147	$243.61	$243.60	$243.60
Purchase #3	$41.61	4.698%	$43.5648	$43.56	$43.55	$43.60
Purchase #4	$29.58	10.820%	$32.7806	$32.78	$32.80	$32.80
Purchase #5	$152.95	4.706%	$160.1478	$160.15	$160.15	$160.10
Purchase #6	$107.61	4.588%	$112.5471	$112.55	$112.55	$112.50
Purchase #7	$112.91	10.768%	$125.0681	$125.07	$125.05	$125.10
7 purchase totals =	$915.54		$987.5510	$987.55	$987.55	$987.50