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	$102.67	6.712%	$109.5612	$109.56	$109.55	$109.60
Purchase #2	$32.49	12.428%	$36.5279	$36.53	$36.55	$36.50
Purchase #3	$114.44	12.639%	$128.9041	$128.90	$128.90	$128.90
Purchase #4	$32.43	3.726%	$33.6383	$33.64	$33.65	$33.60
Purchase #5	$185.84	5.718%	$196.4663	$196.47	$196.45	$196.50
Purchase #6	$205.99	11.297%	$229.2607	$229.26	$229.25	$229.30
Purchase #7	$85.47	3.241%	$88.2401	$88.24	$88.25	$88.20
7 purchase totals =	$759.33		$822.5986	$822.60	$822.60	$822.60