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	$223.59	8.179%	$241.8774	$241.88	$241.90	$241.90
Purchase #2	$79.79	12.133%	$89.4709	$89.47	$89.45	$89.50
Purchase #3	$20.76	8.803%	$22.5875	$22.59	$22.60	$22.60
Purchase #4	$55.72	5.330%	$58.6899	$58.69	$58.70	$58.70
Purchase #5	$57.43	12.647%	$64.6932	$64.69	$64.70	$64.70
Purchase #6	$222.67	13.675%	$253.1201	$253.12	$253.10	$253.10
Purchase #7	$161.64	13.773%	$183.9027	$183.90	$183.90	$183.90
7 purchase totals =	$821.60		$914.3417	$914.34	$914.35	$914.40