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	$64.81	12.155%	$72.6877	$72.69	$72.70	$72.70
Purchase #2	$184.86	6.334%	$196.569	$196.57	$196.55	$196.60
Purchase #3	$36.84	12.629%	$41.4925	$41.49	$41.50	$41.50
Purchase #4	$126.33	13.408%	$143.2683	$143.27	$143.25	$143.30
Purchase #5	$49.73	12.572%	$55.9821	$55.98	$56.00	$56.00
Purchase #6	$199.75	12.409%	$224.537	$224.54	$224.55	$224.50
Purchase #7	$182.35	3.563%	$188.8471	$188.85	$188.85	$188.80
7 purchase totals =	$844.67		$923.3837	$923.39	$923.40	$923.40