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	$37.94	9.391%	$41.5029	$41.50	$41.50	$41.50
Purchase #2	$86.95	9.661%	$95.3502	$95.35	$95.35	$95.40
Purchase #3	$34.88	8.615%	$37.8849	$37.88	$37.90	$37.90
Purchase #4	$147.46	5.386%	$155.4022	$155.40	$155.40	$155.40
Purchase #5	$97.55	11.134%	$108.4112	$108.41	$108.40	$108.40
Purchase #6	$39.98	11.524%	$44.5873	$44.59	$44.60	$44.60
Purchase #7	$193.83	13.658%	$220.3033	$220.30	$220.30	$220.30
7 purchase totals =	$638.59		$703.4420	$703.43	$703.45	$703.50