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	$92.82	10.859%	$102.8993	$102.90	$102.90	$102.90
Purchase #2	$59.58	12.471%	$67.0102	$67.01	$67.00	$67.00
Purchase #3	$102.46	3.573%	$106.1209	$106.12	$106.10	$106.10
Purchase #4	$153.85	12.253%	$172.7012	$172.70	$172.70	$172.70
Purchase #5	$80.30	8.195%	$86.8806	$86.88	$86.90	$86.90
Purchase #6	$106.26	6.388%	$113.0479	$113.05	$113.05	$113.00
Purchase #7	$223.55	13.737%	$254.2591	$254.26	$254.25	$254.30
7 purchase totals =	$818.82		$902.9192	$902.92	$902.90	$902.90