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	$241.29	5.655%	$254.9349	$254.93	$254.95	$254.90
Purchase #2	$189.86	3.712%	$196.9076	$196.91	$196.90	$196.90
Purchase #3	$250.61	9.816%	$275.2099	$275.21	$275.20	$275.20
Purchase #4	$6.63	4.135%	$6.9042	$6.90	$6.90	$6.90
Purchase #5	$61.79	6.820%	$66.0041	$66.00	$66.00	$66.00
Purchase #6	$175.48	4.800%	$183.903	$183.90	$183.90	$183.90
Purchase #7	$164.94	6.552%	$175.7469	$175.75	$175.75	$175.70
7 purchase totals =	$1,090.60		$1,159.6106	$1,159.60	$1,159.60	$1,159.50