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	$41.83	6.505%	$44.551	$44.55	$44.55	$44.60
Purchase #2	$246.33	13.710%	$280.1018	$280.10	$280.10	$280.10
Purchase #3	$193.32	9.233%	$211.1692	$211.17	$211.15	$211.20
Purchase #4	$64.68	5.823%	$68.4463	$68.45	$68.45	$68.40
Purchase #5	$212.35	10.611%	$234.8825	$234.88	$234.90	$234.90
Purchase #6	$42.27	3.458%	$43.7317	$43.73	$43.75	$43.70
Purchase #7	$113.33	12.644%	$127.6594	$127.66	$127.65	$127.70
7 purchase totals =	$914.11		$1,010.5419	$1,010.54	$1,010.55	$1,010.60