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	$41.68	9.543%	$45.6575	$45.66	$45.65	$45.70
Purchase #2	$73.36	4.368%	$76.5644	$76.56	$76.55	$76.60
Purchase #3	$48.61	5.847%	$51.4522	$51.45	$51.45	$51.50
Purchase #4	$30.30	3.388%	$31.3266	$31.33	$31.35	$31.30
Purchase #5	$56.60	7.827%	$61.0301	$61.03	$61.05	$61.00
Purchase #6	$98.76	3.408%	$102.1257	$102.13	$102.15	$102.10
Purchase #7	$126.46	3.305%	$130.6395	$130.64	$130.65	$130.60
7 purchase totals =	$475.77		$498.7960	$498.80	$498.85	$498.80