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	$187.84	4.871%	$196.9897	$196.99	$197.00	$197.00
Purchase #2	$134.73	6.788%	$143.8755	$143.88	$143.90	$143.90
Purchase #3	$103.32	8.246%	$111.8398	$111.84	$111.85	$111.80
Purchase #4	$24.27	9.243%	$26.5133	$26.51	$26.50	$26.50
Purchase #5	$89.67	9.241%	$97.9564	$97.96	$97.95	$98.00
Purchase #6	$32.25	9.535%	$35.325	$35.33	$35.35	$35.30
Purchase #7	$69.26	12.510%	$77.9244	$77.92	$77.90	$77.90
7 purchase totals =	$641.34		$690.4241	$690.43	$690.45	$690.40