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	$66.51	4.366%	$69.4138	$69.41	$69.40	$69.40
Purchase #2	$33.25	11.362%	$37.0279	$37.03	$37.05	$37.00
Purchase #3	$115.32	13.704%	$131.1235	$131.12	$131.10	$131.10
Purchase #4	$78.47	9.503%	$85.927	$85.93	$85.95	$85.90
Purchase #5	$51.67	3.258%	$53.3534	$53.35	$53.35	$53.40
Purchase #6	$13.64	6.639%	$14.5456	$14.55	$14.55	$14.50
Purchase #7	$84.84	3.740%	$88.013	$88.01	$88.00	$88.00
7 purchase totals =	$443.70		$479.4042	$479.40	$479.40	$479.30