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	$22.36	10.423%	$24.6906	$24.69	$24.70	$24.70
Purchase #2	$118.96	6.677%	$126.903	$126.90	$126.90	$126.90
Purchase #3	$85.76	12.553%	$96.5255	$96.53	$96.55	$96.50
Purchase #4	$59.79	12.220%	$67.0963	$67.10	$67.10	$67.10
Purchase #5	$71.82	8.637%	$78.0231	$78.02	$78.00	$78.00
Purchase #6	$32.84	11.547%	$36.632	$36.63	$36.65	$36.60
Purchase #7	$66.55	9.559%	$72.9115	$72.91	$72.90	$72.90
7 purchase totals =	$458.08		$502.7820	$502.78	$502.80	$502.70