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	$217.33	6.630%	$231.739	$231.74	$231.75	$231.70
Purchase #2	$240.26	6.107%	$254.9327	$254.93	$254.95	$254.90
Purchase #3	$218.91	11.273%	$243.5877	$243.59	$243.60	$243.60
Purchase #4	$59.47	12.434%	$66.8645	$66.86	$66.85	$66.90
Purchase #5	$92.72	13.704%	$105.4263	$105.43	$105.45	$105.40
Purchase #6	$72.34	4.349%	$75.4861	$75.49	$75.50	$75.50
Purchase #7	$229.28	6.498%	$244.1786	$244.18	$244.20	$244.20
7 purchase totals =	$1,130.31		$1,222.2149	$1,222.22	$1,222.30	$1,222.20