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	$215.35	8.307%	$233.2391	$233.24	$233.25	$233.20
Purchase #2	$185.48	11.148%	$206.1573	$206.16	$206.15	$206.20
Purchase #3	$204.69	8.401%	$221.886	$221.89	$221.90	$221.90
Purchase #4	$31.73	10.553%	$35.0785	$35.08	$35.10	$35.10
Purchase #5	$145.35	7.774%	$156.6495	$156.65	$156.65	$156.60
Purchase #6	$198.74	13.235%	$225.0432	$225.04	$225.05	$225.00
Purchase #7	$80.86	10.745%	$89.5484	$89.55	$89.55	$89.50
7 purchase totals =	$1,062.20		$1,167.6020	$1,167.61	$1,167.65	$1,167.50