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	$171.40	8.824%	$186.5243	$186.52	$186.50	$186.50
Purchase #2	$216.49	10.394%	$238.992	$238.99	$239.00	$239.00
Purchase #3	$92.46	9.651%	$101.3833	$101.38	$101.40	$101.40
Purchase #4	$95.54	10.554%	$105.6233	$105.62	$105.60	$105.60
Purchase #5	$162.54	11.743%	$181.6271	$181.63	$181.65	$181.60
Purchase #6	$44.88	6.649%	$47.8641	$47.86	$47.85	$47.90
Purchase #7	$158.92	8.377%	$172.2327	$172.23	$172.25	$172.20
7 purchase totals =	$942.23		$1,034.2468	$1,034.23	$1,034.25	$1,034.20