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	$197.45	6.578%	$210.4383	$210.44	$210.45	$210.40
Purchase #2	$149.73	10.153%	$164.9321	$164.93	$164.95	$164.90
Purchase #3	$39.36	6.142%	$41.7775	$41.78	$41.80	$41.80
Purchase #4	$85.30	12.544%	$96	$96.00	$96.00	$96.00
Purchase #5	$152.29	13.270%	$172.4989	$172.50	$172.50	$172.50
Purchase #6	$103.44	12.855%	$116.7372	$116.74	$116.75	$116.70
Purchase #7	$17.33	4.796%	$18.1611	$18.16	$18.15	$18.20
7 purchase totals =	$744.90		$820.5451	$820.55	$820.60	$820.50