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	$30.46	7.619%	$32.7807	$32.78	$32.80	$32.80
Purchase #2	$234.89	10.556%	$259.685	$259.69	$259.70	$259.70
Purchase #3	$199.77	12.392%	$224.5255	$224.53	$224.55	$224.50
Purchase #4	$181.41	13.313%	$205.5611	$205.56	$205.55	$205.60
Purchase #5	$225.52	6.785%	$240.8215	$240.82	$240.80	$240.80
Purchase #6	$79.36	5.504%	$83.728	$83.73	$83.75	$83.70
Purchase #7	$94.50	3.454%	$97.764	$97.76	$97.75	$97.80
7 purchase totals =	$1,045.91		$1,144.8658	$1,144.87	$1,144.90	$1,144.90