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	$173.37	7.176%	$185.811	$185.81	$185.80	$185.80
Purchase #2	$227.42	3.242%	$234.793	$234.79	$234.80	$234.80
Purchase #3	$209.27	10.777%	$231.823	$231.82	$231.80	$231.80
Purchase #4	$63.32	7.179%	$67.8657	$67.87	$67.85	$67.90
Purchase #5	$61.73	8.637%	$67.0616	$67.06	$67.05	$67.10
Purchase #6	$76.39	3.733%	$79.2416	$79.24	$79.25	$79.20
Purchase #7	$126.61	10.404%	$139.7825	$139.78	$139.80	$139.80
7 purchase totals =	$938.11		$1,006.3784	$1,006.37	$1,006.35	$1,006.40