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	$164.63	8.662%	$178.8903	$178.89	$178.90	$178.90
Purchase #2	$121.69	7.819%	$131.2049	$131.20	$131.20	$131.20
Purchase #3	$230.41	6.835%	$246.1585	$246.16	$246.15	$246.20
Purchase #4	$202.43	6.153%	$214.8855	$214.89	$214.90	$214.90
Purchase #5	$64.33	6.321%	$68.3963	$68.40	$68.40	$68.40
Purchase #6	$162.78	7.791%	$175.4622	$175.46	$175.45	$175.50
Purchase #7	$41.85	10.532%	$46.2576	$46.26	$46.25	$46.30
7 purchase totals =	$988.12		$1,061.2553	$1,061.26	$1,061.25	$1,061.40