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	$238.59	11.419%	$265.8346	$265.83	$265.85	$265.80
Purchase #2	$188.49	4.768%	$197.4772	$197.48	$197.50	$197.50
Purchase #3	$70.25	3.797%	$72.9174	$72.92	$72.90	$72.90
Purchase #4	$33.53	10.431%	$37.0275	$37.03	$37.05	$37.00
Purchase #5	$245.51	6.302%	$260.982	$260.98	$261.00	$261.00
Purchase #6	$87.85	3.300%	$90.7491	$90.75	$90.75	$90.70
Purchase #7	$82.47	12.426%	$92.7177	$92.72	$92.70	$92.70
7 purchase totals =	$946.69		$1,017.7055	$1,017.71	$1,017.75	$1,017.60