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	$132.72	11.131%	$147.4931	$147.49	$147.50	$147.50
Purchase #2	$206.91	3.187%	$213.5042	$213.50	$213.50	$213.50
Purchase #3	$199.69	11.306%	$222.267	$222.27	$222.25	$222.30
Purchase #4	$56.42	12.567%	$63.5103	$63.51	$63.50	$63.50
Purchase #5	$59.47	5.393%	$62.6772	$62.68	$62.70	$62.70
Purchase #6	$32.36	12.252%	$36.3247	$36.32	$36.30	$36.30
Purchase #7	$82.28	7.407%	$88.3745	$88.37	$88.35	$88.40
7 purchase totals =	$769.85		$834.1510	$834.14	$834.10	$834.20