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	$211.40	5.154%	$222.2956	$222.30	$222.30	$222.30
Purchase #2	$18.75	5.115%	$19.7091	$19.71	$19.70	$19.70
Purchase #3	$196.75	9.600%	$215.638	$215.64	$215.65	$215.60
Purchase #4	$195.87	13.560%	$222.43	$222.43	$222.45	$222.40
Purchase #5	$148.95	7.128%	$159.5672	$159.57	$159.55	$159.60
Purchase #6	$17.96	12.258%	$20.1615	$20.16	$20.15	$20.20
Purchase #7	$100.59	12.230%	$112.8922	$112.89	$112.90	$112.90
7 purchase totals =	$890.27		$972.6936	$972.70	$972.70	$972.70