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	$135.68	12.638%	$152.8272	$152.83	$152.85	$152.80
Purchase #2	$153.48	8.271%	$166.1743	$166.17	$166.15	$166.20
Purchase #3	$143.68	12.813%	$162.0897	$162.09	$162.10	$162.10
Purchase #4	$153.52	6.147%	$162.9569	$162.96	$162.95	$163.00
Purchase #5	$169.28	5.231%	$178.135	$178.14	$178.15	$178.10
Purchase #6	$92.99	8.461%	$100.8579	$100.86	$100.85	$100.90
Purchase #7	$126.53	11.302%	$140.8304	$140.83	$140.85	$140.80
7 purchase totals =	$975.16		$1,063.8714	$1,063.88	$1,063.90	$1,063.90