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	$53.41	6.525%	$56.895	$56.90	$56.90	$56.90
Purchase #2	$181.54	12.651%	$204.5066	$204.51	$204.50	$204.50
Purchase #3	$49.41	10.691%	$54.6924	$54.69	$54.70	$54.70
Purchase #4	$148.77	11.181%	$165.404	$165.40	$165.40	$165.40
Purchase #5	$188.38	8.705%	$204.7785	$204.78	$204.80	$204.80
Purchase #6	$230.85	3.411%	$238.7243	$238.72	$238.70	$238.70
Purchase #7	$113.96	8.259%	$123.372	$123.37	$123.35	$123.40
7 purchase totals =	$966.32		$1,048.3728	$1,048.37	$1,048.35	$1,048.40