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	$105.61	11.410%	$117.6601	$117.66	$117.65	$117.70
Purchase #2	$86.69	12.533%	$97.5549	$97.55	$97.55	$97.60
Purchase #3	$189.63	3.109%	$195.5256	$195.53	$195.55	$195.50
Purchase #4	$24.91	11.320%	$27.7298	$27.73	$27.75	$27.70
Purchase #5	$79.69	12.310%	$89.4998	$89.50	$89.50	$89.50
Purchase #6	$250.67	9.446%	$274.3483	$274.35	$274.35	$274.30
Purchase #7	$89.40	11.523%	$99.7016	$99.70	$99.70	$99.70
7 purchase totals =	$826.60		$902.0201	$902.02	$902.05	$902.00