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	$154.39	11.647%	$172.3718	$172.37	$172.35	$172.40
Purchase #2	$54.75	8.500%	$59.4038	$59.40	$59.40	$59.40
Purchase #3	$204.73	3.386%	$211.6622	$211.66	$211.65	$211.70
Purchase #4	$28.31	10.263%	$31.2155	$31.22	$31.20	$31.20
Purchase #5	$162.54	11.585%	$181.3703	$181.37	$181.35	$181.40
Purchase #6	$238.79	7.323%	$256.2766	$256.28	$256.30	$256.30
Purchase #7	$148.49	10.399%	$163.9315	$163.93	$163.95	$163.90
7 purchase totals =	$992.00		$1,076.2317	$1,076.23	$1,076.20	$1,076.30