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	$172.38	11.310%	$191.8762	$191.88	$191.90	$191.90
Purchase #2	$77.95	12.553%	$87.7351	$87.74	$87.75	$87.70
Purchase #3	$49.83	12.195%	$55.9068	$55.91	$55.90	$55.90
Purchase #4	$159.76	13.231%	$180.8978	$180.90	$180.90	$180.90
Purchase #5	$146.96	11.567%	$163.9589	$163.96	$163.95	$164.00
Purchase #6	$81.86	10.167%	$90.1827	$90.18	$90.20	$90.20
Purchase #7	$220.39	10.666%	$243.8968	$243.90	$243.90	$243.90
7 purchase totals =	$909.13		$1,014.4543	$1,014.47	$1,014.50	$1,014.50