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	$61.33	5.802%	$64.8884	$64.89	$64.90	$64.90
Purchase #2	$91.87	7.401%	$98.6693	$98.67	$98.65	$98.70
Purchase #3	$241.65	6.619%	$257.6448	$257.64	$257.65	$257.60
Purchase #4	$73.33	8.359%	$79.4597	$79.46	$79.45	$79.50
Purchase #5	$55.56	7.344%	$59.6403	$59.64	$59.65	$59.60
Purchase #6	$134.28	5.859%	$142.1475	$142.15	$142.15	$142.10
Purchase #7	$63.46	10.164%	$69.9101	$69.91	$69.90	$69.90
7 purchase totals =	$721.48		$772.3601	$772.36	$772.35	$772.30