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	$93.36	11.704%	$104.2869	$104.29	$104.30	$104.30
Purchase #2	$139.25	4.726%	$145.831	$145.83	$145.85	$145.80
Purchase #3	$164.80	4.409%	$172.066	$172.07	$172.05	$172.10
Purchase #4	$178.81	9.792%	$196.3191	$196.32	$196.30	$196.30
Purchase #5	$88.38	5.443%	$93.1905	$93.19	$93.20	$93.20
Purchase #6	$180.73	7.679%	$194.6083	$194.61	$194.60	$194.60
Purchase #7	$196.82	3.330%	$203.3741	$203.37	$203.35	$203.40
7 purchase totals =	$1,042.15		$1,109.6759	$1,109.68	$1,109.65	$1,109.70