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	$110.82	13.608%	$125.9004	$125.90	$125.90	$125.90
Purchase #2	$134.80	12.435%	$151.5624	$151.56	$151.55	$151.60
Purchase #3	$25.28	9.136%	$27.5896	$27.59	$27.60	$27.60
Purchase #4	$120.89	12.326%	$135.7909	$135.79	$135.80	$135.80
Purchase #5	$64.40	11.171%	$71.5941	$71.59	$71.60	$71.60
Purchase #6	$25.46	13.845%	$28.9849	$28.98	$29.00	$29.00
Purchase #7	$128.48	9.275%	$140.3965	$140.40	$140.40	$140.40
7 purchase totals =	$610.13		$681.8188	$681.81	$681.85	$681.90