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	$159.46	5.442%	$168.1378	$168.14	$168.15	$168.10
Purchase #2	$184.81	3.721%	$191.6868	$191.69	$191.70	$191.70
Purchase #3	$53.39	5.125%	$56.1262	$56.13	$56.15	$56.10
Purchase #4	$52.83	7.815%	$56.9587	$56.96	$56.95	$57.00
Purchase #5	$99.80	5.703%	$105.4916	$105.49	$105.50	$105.50
Purchase #6	$170.81	10.324%	$188.4444	$188.44	$188.45	$188.40
Purchase #7	$222.61	5.237%	$234.2681	$234.27	$234.25	$234.30
7 purchase totals =	$943.71		$1,001.1136	$1,001.12	$1,001.15	$1,001.10