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	$92.99	12.757%	$104.8527	$104.85	$104.85	$104.90
Purchase #2	$37.51	7.107%	$40.1758	$40.18	$40.20	$40.20
Purchase #3	$115.88	7.747%	$124.8572	$124.86	$124.85	$124.90
Purchase #4	$192.96	11.714%	$215.5633	$215.56	$215.55	$215.60
Purchase #5	$155.48	13.466%	$176.4169	$176.42	$176.40	$176.40
Purchase #6	$85.43	13.386%	$96.8657	$96.87	$96.85	$96.90
Purchase #7	$242.27	7.179%	$259.6626	$259.66	$259.65	$259.70
7 purchase totals =	$922.52		$1,018.3942	$1,018.40	$1,018.35	$1,018.60