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	$205.25	8.414%	$222.5197	$222.52	$222.50	$222.50
Purchase #2	$8.45	11.797%	$9.4468	$9.45	$9.45	$9.40
Purchase #3	$56.35	6.710%	$60.1311	$60.13	$60.15	$60.10
Purchase #4	$109.43	7.224%	$117.3352	$117.34	$117.35	$117.30
Purchase #5	$179.49	9.694%	$196.8898	$196.89	$196.90	$196.90
Purchase #6	$68.57	5.425%	$72.2899	$72.29	$72.30	$72.30
Purchase #7	$233.31	4.283%	$243.3027	$243.30	$243.30	$243.30
7 purchase totals =	$860.85		$921.9152	$921.92	$921.95	$921.80