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	$110.61	8.138%	$119.6114	$119.61	$119.60	$119.60
Purchase #2	$203.63	9.413%	$222.7977	$222.80	$222.80	$222.80
Purchase #3	$225.40	9.707%	$247.2796	$247.28	$247.30	$247.30
Purchase #4	$73.74	6.812%	$78.7632	$78.76	$78.75	$78.80
Purchase #5	$66.80	12.269%	$74.9957	$75.00	$75.00	$75.00
Purchase #6	$31.92	5.342%	$33.6252	$33.63	$33.65	$33.60
Purchase #7	$94.64	6.156%	$100.466	$100.47	$100.45	$100.50
7 purchase totals =	$806.74		$877.5388	$877.55	$877.55	$877.60