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	$175.59	5.421%	$185.1087	$185.11	$185.10	$185.10
Purchase #2	$35.93	13.157%	$40.6573	$40.66	$40.65	$40.70
Purchase #3	$62.62	6.847%	$66.9076	$66.91	$66.90	$66.90
Purchase #4	$181.60	5.442%	$191.4827	$191.48	$191.50	$191.50
Purchase #5	$48.98	5.735%	$51.789	$51.79	$51.80	$51.80
Purchase #6	$50.67	7.728%	$54.5858	$54.59	$54.60	$54.60
Purchase #7	$220.94	10.632%	$244.4303	$244.43	$244.45	$244.40
7 purchase totals =	$776.33		$834.9614	$834.97	$835.00	$835.00