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	$104.91	3.563%	$108.6479	$108.65	$108.65	$108.60
Purchase #2	$65.64	3.225%	$67.7569	$67.76	$67.75	$67.80
Purchase #3	$219.94	6.271%	$233.7324	$233.73	$233.75	$233.70
Purchase #4	$58.94	9.573%	$64.5823	$64.58	$64.60	$64.60
Purchase #5	$43.99	7.221%	$47.1665	$47.17	$47.15	$47.20
Purchase #6	$76.39	7.725%	$82.2911	$82.29	$82.30	$82.30
Purchase #7	$63.96	13.125%	$72.3548	$72.35	$72.35	$72.40
7 purchase totals =	$633.77		$676.5319	$676.53	$676.55	$676.60