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	$214.33	6.796%	$228.8959	$228.90	$228.90	$228.90
Purchase #2	$191.51	10.859%	$212.3061	$212.31	$212.30	$212.30
Purchase #3	$54.52	9.169%	$59.5189	$59.52	$59.50	$59.50
Purchase #4	$224.51	7.298%	$240.8947	$240.89	$240.90	$240.90
Purchase #5	$12.61	8.794%	$13.7189	$13.72	$13.70	$13.70
Purchase #6	$82.71	3.615%	$85.7	$85.70	$85.70	$85.70
Purchase #7	$171.91	10.818%	$190.5072	$190.51	$190.50	$190.50
7 purchase totals =	$952.10		$1,031.5417	$1,031.55	$1,031.50	$1,031.50