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	$156.36	12.490%	$175.8894	$175.89	$175.90	$175.90
Purchase #2	$23.47	8.816%	$25.5391	$25.54	$25.55	$25.50
Purchase #3	$92.88	3.759%	$96.3714	$96.37	$96.35	$96.40
Purchase #4	$85.27	11.786%	$95.3199	$95.32	$95.30	$95.30
Purchase #5	$180.91	8.830%	$196.8844	$196.88	$196.90	$196.90
Purchase #6	$106.50	10.531%	$117.7155	$117.72	$117.70	$117.70
Purchase #7	$188.45	11.634%	$210.3743	$210.37	$210.35	$210.40
7 purchase totals =	$833.84		$918.0940	$918.09	$918.05	$918.10