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	$192.46	13.732%	$218.8886	$218.89	$218.90	$218.90
Purchase #2	$47.64	6.845%	$50.901	$50.90	$50.90	$50.90
Purchase #3	$6.97	12.717%	$7.8564	$7.86	$7.85	$7.90
Purchase #4	$40.28	6.802%	$43.0198	$43.02	$43.00	$43.00
Purchase #5	$46.61	12.551%	$52.46	$52.46	$52.45	$52.50
Purchase #6	$158.76	4.386%	$165.7232	$165.72	$165.70	$165.70
Purchase #7	$194.82	9.310%	$212.9577	$212.96	$212.95	$213.00
7 purchase totals =	$687.54		$751.8067	$751.81	$751.75	$751.90