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	$92.42	12.165%	$103.6629	$103.66	$103.65	$103.70
Purchase #2	$203.88	3.665%	$211.3522	$211.35	$211.35	$211.40
Purchase #3	$170.25	9.505%	$186.4323	$186.43	$186.45	$186.40
Purchase #4	$118.60	8.371%	$128.528	$128.53	$128.55	$128.50
Purchase #5	$193.80	3.422%	$200.4318	$200.43	$200.45	$200.40
Purchase #6	$138.58	9.487%	$151.7271	$151.73	$151.75	$151.70
Purchase #7	$87.56	13.368%	$99.265	$99.27	$99.25	$99.30
7 purchase totals =	$1,005.09		$1,081.3993	$1,081.40	$1,081.45	$1,081.40