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	$76.80	12.568%	$86.4522	$86.45	$86.45	$86.50
Purchase #2	$222.87	5.340%	$234.7713	$234.77	$234.75	$234.80
Purchase #3	$224.89	5.866%	$238.082	$238.08	$238.10	$238.10
Purchase #4	$33.85	11.347%	$37.691	$37.69	$37.70	$37.70
Purchase #5	$192.85	4.145%	$200.8436	$200.84	$200.85	$200.80
Purchase #6	$133.72	6.585%	$142.5255	$142.53	$142.55	$142.50
Purchase #7	$92.53	4.745%	$96.9205	$96.92	$96.90	$96.90
7 purchase totals =	$977.51		$1,037.2861	$1,037.28	$1,037.30	$1,037.30