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	$78.76	10.513%	$87.04	$87.04	$87.05	$87.00
Purchase #2	$12.39	4.767%	$12.9806	$12.98	$13.00	$13.00
Purchase #3	$136.77	4.378%	$142.7578	$142.76	$142.75	$142.80
Purchase #4	$81.41	8.734%	$88.5203	$88.52	$88.50	$88.50
Purchase #5	$242.85	9.437%	$265.7678	$265.77	$265.75	$265.80
Purchase #6	$124.75	13.427%	$141.5002	$141.50	$141.50	$141.50
Purchase #7	$64.98	4.485%	$67.8944	$67.89	$67.90	$67.90
7 purchase totals =	$741.91		$806.4611	$806.46	$806.45	$806.50