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	$181.84	5.497%	$191.8357	$191.84	$191.85	$191.80
Purchase #2	$55.81	12.120%	$62.5742	$62.57	$62.55	$62.60
Purchase #3	$83.87	6.710%	$89.4977	$89.50	$89.50	$89.50
Purchase #4	$54.55	8.200%	$59.0231	$59.02	$59.00	$59.00
Purchase #5	$55.37	9.401%	$60.5753	$60.58	$60.60	$60.60
Purchase #6	$55.30	3.674%	$57.3317	$57.33	$57.35	$57.30
Purchase #7	$196.76	9.212%	$214.8855	$214.89	$214.90	$214.90
7 purchase totals =	$683.50		$735.7232	$735.73	$735.75	$735.70