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	$202.63	6.542%	$215.8861	$215.89	$215.90	$215.90
Purchase #2	$105.98	13.864%	$120.6731	$120.67	$120.65	$120.70
Purchase #3	$245.82	7.628%	$264.5711	$264.57	$264.55	$264.60
Purchase #4	$128.51	8.655%	$139.6325	$139.63	$139.65	$139.60
Purchase #5	$36.45	10.836%	$40.3997	$40.40	$40.40	$40.40
Purchase #6	$167.81	7.229%	$179.941	$179.94	$179.95	$179.90
Purchase #7	$47.90	11.432%	$53.3759	$53.38	$53.40	$53.40
7 purchase totals =	$935.10		$1,014.4794	$1,014.48	$1,014.50	$1,014.50