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	$64.98	7.510%	$69.86	$69.86	$69.85	$69.90
Purchase #2	$185.94	6.105%	$197.2916	$197.29	$197.30	$197.30
Purchase #3	$103.43	5.623%	$109.2459	$109.25	$109.25	$109.20
Purchase #4	$171.30	13.139%	$193.8071	$193.81	$193.80	$193.80
Purchase #5	$136.51	13.446%	$154.8651	$154.87	$154.85	$154.90
Purchase #6	$190.89	11.834%	$213.4799	$213.48	$213.50	$213.50
Purchase #7	$173.61	10.537%	$191.9033	$191.90	$191.90	$191.90
7 purchase totals =	$1,026.66		$1,130.4529	$1,130.46	$1,130.45	$1,130.50