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	$187.41	11.191%	$208.3831	$208.38	$208.40	$208.40
Purchase #2	$131.39	11.656%	$146.7048	$146.70	$146.70	$146.70
Purchase #3	$56.31	13.405%	$63.8584	$63.86	$63.85	$63.90
Purchase #4	$46.86	8.181%	$50.6936	$50.69	$50.70	$50.70
Purchase #5	$63.93	12.607%	$71.9897	$71.99	$72.00	$72.00
Purchase #6	$35.45	8.649%	$38.5161	$38.52	$38.50	$38.50
Purchase #7	$90.98	13.538%	$103.2969	$103.30	$103.30	$103.30
7 purchase totals =	$612.33		$683.4426	$683.44	$683.45	$683.50