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	$119.87	6.320%	$127.4458	$127.45	$127.45	$127.40
Purchase #2	$193.72	4.515%	$202.4665	$202.47	$202.45	$202.50
Purchase #3	$33.48	4.676%	$35.0455	$35.05	$35.05	$35.00
Purchase #4	$87.65	13.432%	$99.4231	$99.42	$99.40	$99.40
Purchase #5	$73.64	3.761%	$76.4096	$76.41	$76.40	$76.40
Purchase #6	$96.35	9.271%	$105.2826	$105.28	$105.30	$105.30
Purchase #7	$110.47	7.233%	$118.4603	$118.46	$118.45	$118.50
7 purchase totals =	$715.18		$764.5334	$764.54	$764.50	$764.50