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	$131.47	10.666%	$145.4926	$145.49	$145.50	$145.50
Purchase #2	$74.60	4.279%	$77.7921	$77.79	$77.80	$77.80
Purchase #3	$154.57	8.620%	$167.8939	$167.89	$167.90	$167.90
Purchase #4	$38.44	7.200%	$41.2077	$41.21	$41.20	$41.20
Purchase #5	$180.35	6.199%	$191.5299	$191.53	$191.55	$191.50
Purchase #6	$176.65	11.249%	$196.5214	$196.52	$196.50	$196.50
Purchase #7	$228.25	3.286%	$235.7503	$235.75	$235.75	$235.80
7 purchase totals =	$984.33		$1,056.1879	$1,056.18	$1,056.20	$1,056.20