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	$207.61	13.844%	$236.3515	$236.35	$236.35	$236.40
Purchase #2	$233.64	13.663%	$265.5622	$265.56	$265.55	$265.60
Purchase #3	$114.90	4.160%	$119.6798	$119.68	$119.70	$119.70
Purchase #4	$125.65	12.314%	$141.1225	$141.12	$141.10	$141.10
Purchase #5	$182.32	5.191%	$191.7842	$191.78	$191.80	$191.80
Purchase #6	$206.83	7.568%	$222.4829	$222.48	$222.50	$222.50
Purchase #7	$12.32	7.762%	$13.2763	$13.28	$13.30	$13.30
7 purchase totals =	$1,083.27		$1,190.2594	$1,190.25	$1,190.30	$1,190.40