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	$7.27	7.590%	$7.8218	$7.82	$7.80	$7.80
Purchase #2	$77.87	10.394%	$85.9638	$85.96	$85.95	$86.00
Purchase #3	$246.99	4.816%	$258.885	$258.89	$258.90	$258.90
Purchase #4	$17.82	10.586%	$19.7064	$19.71	$19.70	$19.70
Purchase #5	$56.36	9.589%	$61.7644	$61.76	$61.75	$61.80
Purchase #6	$108.64	9.192%	$118.6262	$118.63	$118.65	$118.60
Purchase #7	$104.74	9.743%	$114.9448	$114.94	$114.95	$114.90
7 purchase totals =	$619.69		$667.7124	$667.71	$667.70	$667.70