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	$211.28	3.335%	$218.3262	$218.33	$218.35	$218.30
Purchase #2	$182.73	12.679%	$205.8983	$205.90	$205.90	$205.90
Purchase #3	$192.79	9.414%	$210.9393	$210.94	$210.95	$210.90
Purchase #4	$116.36	9.617%	$127.5503	$127.55	$127.55	$127.60
Purchase #5	$90.96	5.391%	$95.8637	$95.86	$95.85	$95.90
Purchase #6	$59.85	13.372%	$67.8531	$67.85	$67.85	$67.90
Purchase #7	$248.81	8.717%	$270.4988	$270.50	$270.50	$270.50
7 purchase totals =	$1,102.78		$1,196.9297	$1,196.93	$1,196.95	$1,197.00