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	$92.38	11.436%	$102.9446	$102.94	$102.95	$102.90
Purchase #2	$185.65	10.537%	$205.2119	$205.21	$205.20	$205.20
Purchase #3	$139.34	8.664%	$151.4124	$151.41	$151.40	$151.40
Purchase #4	$55.53	10.422%	$61.3173	$61.32	$61.30	$61.30
Purchase #5	$19.95	3.245%	$20.5974	$20.60	$20.60	$20.60
Purchase #6	$152.60	7.645%	$164.2663	$164.27	$164.25	$164.30
Purchase #7	$44.55	3.218%	$45.9836	$45.98	$46.00	$46.00
7 purchase totals =	$690.00		$751.7335	$751.73	$751.70	$751.70