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	$31.47	5.745%	$33.278	$33.28	$33.30	$33.30
Purchase #2	$84.57	5.107%	$88.889	$88.89	$88.90	$88.90
Purchase #3	$216.55	3.295%	$223.6853	$223.69	$223.70	$223.70
Purchase #4	$90.66	12.865%	$102.3234	$102.32	$102.30	$102.30
Purchase #5	$134.48	10.424%	$148.4982	$148.50	$148.50	$148.50
Purchase #6	$227.66	6.248%	$241.8842	$241.88	$241.90	$241.90
Purchase #7	$22.39	9.355%	$24.4846	$24.48	$24.50	$24.50
7 purchase totals =	$807.78		$863.0427	$863.04	$863.10	$863.10