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	$190.52	5.261%	$200.5433	$200.54	$200.55	$200.50
Purchase #2	$41.41	3.573%	$42.8896	$42.89	$42.90	$42.90
Purchase #3	$11.33	4.464%	$11.8358	$11.84	$11.85	$11.80
Purchase #4	$32.98	12.709%	$37.1714	$37.17	$37.15	$37.20
Purchase #5	$8.38	11.443%	$9.3389	$9.34	$9.35	$9.30
Purchase #6	$225.92	4.400%	$235.8605	$235.86	$235.85	$235.90
Purchase #7	$111.92	6.396%	$119.0784	$119.08	$119.10	$119.10
7 purchase totals =	$622.46		$656.7179	$656.72	$656.75	$656.70