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	$64.56	10.454%	$71.3091	$71.31	$71.30	$71.30
Purchase #2	$93.72	7.448%	$100.7003	$100.70	$100.70	$100.70
Purchase #3	$185.32	6.293%	$196.9822	$196.98	$197.00	$197.00
Purchase #4	$98.61	5.804%	$104.3333	$104.33	$104.35	$104.30
Purchase #5	$131.79	3.857%	$136.8731	$136.87	$136.85	$136.90
Purchase #6	$44.51	10.807%	$49.3202	$49.32	$49.30	$49.30
Purchase #7	$224.89	9.741%	$246.7965	$246.80	$246.80	$246.80
7 purchase totals =	$843.40		$906.3147	$906.31	$906.30	$906.30