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	$248.39	6.612%	$264.8135	$264.81	$264.80	$264.80
Purchase #2	$181.97	7.863%	$196.2783	$196.28	$196.30	$196.30
Purchase #3	$83.98	6.799%	$89.6898	$89.69	$89.70	$89.70
Purchase #4	$102.87	5.405%	$108.4301	$108.43	$108.45	$108.40
Purchase #5	$62.45	4.228%	$65.0904	$65.09	$65.10	$65.10
Purchase #6	$219.47	5.202%	$230.8868	$230.89	$230.90	$230.90
Purchase #7	$243.86	11.480%	$271.8551	$271.86	$271.85	$271.90
7 purchase totals =	$1,142.99		$1,227.0440	$1,227.05	$1,227.10	$1,227.10