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	$87.80	9.109%	$95.7977	$95.80	$95.80	$95.80
Purchase #2	$236.27	7.260%	$253.4232	$253.42	$253.40	$253.40
Purchase #3	$189.56	12.547%	$213.3441	$213.34	$213.35	$213.30
Purchase #4	$176.88	4.672%	$185.1438	$185.14	$185.15	$185.10
Purchase #5	$188.42	4.513%	$196.9234	$196.92	$196.90	$196.90
Purchase #6	$232.93	9.360%	$254.7322	$254.73	$254.75	$254.70
Purchase #7	$42.88	3.203%	$44.2534	$44.25	$44.25	$44.30
7 purchase totals =	$1,154.74		$1,243.6178	$1,243.60	$1,243.60	$1,243.50