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	$65.39	5.739%	$69.1427	$69.14	$69.15	$69.10
Purchase #2	$31.69	3.840%	$32.9069	$32.91	$32.90	$32.90
Purchase #3	$173.69	10.634%	$192.1602	$192.16	$192.15	$192.20
Purchase #4	$44.71	13.701%	$50.8357	$50.84	$50.85	$50.80
Purchase #5	$50.94	9.800%	$55.9321	$55.93	$55.95	$55.90
Purchase #6	$104.80	12.816%	$118.2312	$118.23	$118.25	$118.20
Purchase #7	$168.71	7.369%	$181.1422	$181.14	$181.15	$181.10
7 purchase totals =	$639.93		$700.3510	$700.35	$700.40	$700.20