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	$119.58	6.457%	$127.3013	$127.30	$127.30	$127.30
Purchase #2	$168.92	11.708%	$188.6972	$188.70	$188.70	$188.70
Purchase #3	$202.32	6.632%	$215.7379	$215.74	$215.75	$215.70
Purchase #4	$177.66	10.342%	$196.0336	$196.03	$196.05	$196.00
Purchase #5	$36.61	5.869%	$38.7586	$38.76	$38.75	$38.80
Purchase #6	$247.31	4.124%	$257.5091	$257.51	$257.50	$257.50
Purchase #7	$139.60	9.127%	$152.3413	$152.34	$152.35	$152.30
7 purchase totals =	$1,092.00		$1,176.3790	$1,176.38	$1,176.40	$1,176.30