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	$174.51	4.164%	$181.7766	$181.78	$181.80	$181.80
Purchase #2	$118.94	10.413%	$131.3252	$131.33	$131.35	$131.30
Purchase #3	$86.74	6.740%	$92.5863	$92.59	$92.60	$92.60
Purchase #4	$136.93	6.280%	$145.5292	$145.53	$145.55	$145.50
Purchase #5	$219.74	4.116%	$228.7845	$228.78	$228.80	$228.80
Purchase #6	$83.54	3.501%	$86.4647	$86.46	$86.45	$86.50
Purchase #7	$232.29	9.799%	$255.0521	$255.05	$255.05	$255.10
7 purchase totals =	$1,052.69		$1,121.5186	$1,121.52	$1,121.60	$1,121.60