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	$55.40	10.621%	$61.284	$61.28	$61.30	$61.30
Purchase #2	$27.83	13.248%	$31.5169	$31.52	$31.50	$31.50
Purchase #3	$145.76	12.586%	$164.1054	$164.11	$164.10	$164.10
Purchase #4	$195.90	7.504%	$210.6003	$210.60	$210.60	$210.60
Purchase #5	$104.84	4.155%	$109.1961	$109.20	$109.20	$109.20
Purchase #6	$206.43	8.757%	$224.5071	$224.51	$224.50	$224.50
Purchase #7	$212.92	13.432%	$241.5194	$241.52	$241.50	$241.50
7 purchase totals =	$949.08		$1,042.7292	$1,042.74	$1,042.70	$1,042.70