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	$98.83	12.870%	$111.5494	$111.55	$111.55	$111.50
Purchase #2	$151.27	9.129%	$165.0794	$165.08	$165.10	$165.10
Purchase #3	$159.93	13.815%	$182.0243	$182.02	$182.00	$182.00
Purchase #4	$62.88	11.828%	$70.3174	$70.32	$70.30	$70.30
Purchase #5	$208.40	12.244%	$233.9165	$233.92	$233.90	$233.90
Purchase #6	$81.58	8.452%	$88.4751	$88.48	$88.50	$88.50
Purchase #7	$131.74	10.726%	$145.8704	$145.87	$145.85	$145.90
7 purchase totals =	$894.63		$997.2325	$997.24	$997.20	$997.20