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	$35.32	4.278%	$36.831	$36.83	$36.85	$36.80
Purchase #2	$223.76	11.587%	$249.6871	$249.69	$249.70	$249.70
Purchase #3	$172.72	10.559%	$190.9575	$190.96	$190.95	$191.00
Purchase #4	$72.78	8.601%	$79.0398	$79.04	$79.05	$79.00
Purchase #5	$235.27	11.633%	$262.639	$262.64	$262.65	$262.60
Purchase #6	$126.52	12.464%	$142.2895	$142.29	$142.30	$142.30
Purchase #7	$147.95	9.825%	$162.4861	$162.49	$162.50	$162.50
7 purchase totals =	$1,014.32		$1,123.9300	$1,123.94	$1,124.00	$1,123.90