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	$247.93	8.245%	$268.3718	$268.37	$268.35	$268.40
Purchase #2	$218.70	10.444%	$241.541	$241.54	$241.55	$241.50
Purchase #3	$135.57	11.292%	$150.8786	$150.88	$150.90	$150.90
Purchase #4	$76.66	13.375%	$86.9133	$86.91	$86.90	$86.90
Purchase #5	$215.76	8.702%	$234.5354	$234.54	$234.55	$234.50
Purchase #6	$110.91	11.463%	$123.6236	$123.62	$123.60	$123.60
Purchase #7	$33.72	8.629%	$36.6297	$36.63	$36.65	$36.60
7 purchase totals =	$1,039.25		$1,142.4934	$1,142.49	$1,142.50	$1,142.40