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	$17.49	8.416%	$18.962	$18.96	$18.95	$19.00
Purchase #2	$189.93	3.413%	$196.4123	$196.41	$196.40	$196.40
Purchase #3	$68.68	12.818%	$77.4834	$77.48	$77.50	$77.50
Purchase #4	$13.50	6.717%	$14.4068	$14.41	$14.40	$14.40
Purchase #5	$196.36	7.707%	$211.4935	$211.49	$211.50	$211.50
Purchase #6	$124.71	5.535%	$131.6127	$131.61	$131.60	$131.60
Purchase #7	$216.94	12.854%	$244.8255	$244.83	$244.85	$244.80
7 purchase totals =	$827.61		$895.1962	$895.19	$895.20	$895.20