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	$150.85	3.430%	$156.0242	$156.02	$156.00	$156.00
Purchase #2	$207.37	5.729%	$219.2502	$219.25	$219.25	$219.30
Purchase #3	$92.40	9.250%	$100.947	$100.95	$100.95	$100.90
Purchase #4	$41.84	10.761%	$46.3424	$46.34	$46.35	$46.30
Purchase #5	$173.56	10.370%	$191.5582	$191.56	$191.55	$191.60
Purchase #6	$184.89	7.403%	$198.5774	$198.58	$198.60	$198.60
Purchase #7	$165.94	3.787%	$172.2241	$172.22	$172.20	$172.20
7 purchase totals =	$1,016.85		$1,084.9235	$1,084.92	$1,084.90	$1,084.90