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	$154.92	11.802%	$173.2037	$173.20	$173.20	$173.20
Purchase #2	$23.89	11.734%	$26.6933	$26.69	$26.70	$26.70
Purchase #3	$187.86	5.488%	$198.1698	$198.17	$198.15	$198.20
Purchase #4	$174.82	9.759%	$191.8807	$191.88	$191.90	$191.90
Purchase #5	$192.96	8.709%	$209.7649	$209.76	$209.75	$209.80
Purchase #6	$94.61	8.792%	$102.9281	$102.93	$102.95	$102.90
Purchase #7	$88.40	12.412%	$99.3722	$99.37	$99.35	$99.40
7 purchase totals =	$917.46		$1,002.0127	$1,002.00	$1,002.00	$1,002.10