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	$105.63	11.749%	$118.0405	$118.04	$118.05	$118.00
Purchase #2	$122.53	13.199%	$138.7027	$138.70	$138.70	$138.70
Purchase #3	$38.31	13.636%	$43.534	$43.53	$43.55	$43.50
Purchase #4	$184.57	13.729%	$209.9096	$209.91	$209.90	$209.90
Purchase #5	$86.72	9.150%	$94.6549	$94.65	$94.65	$94.70
Purchase #6	$122.67	4.192%	$127.8123	$127.81	$127.80	$127.80
Purchase #7	$164.55	10.303%	$181.5036	$181.50	$181.50	$181.50
7 purchase totals =	$824.98		$914.1576	$914.14	$914.15	$914.10