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	$243.53	5.474%	$256.8608	$256.86	$256.85	$256.90
Purchase #2	$65.42	3.172%	$67.4951	$67.50	$67.50	$67.50
Purchase #3	$188.94	12.656%	$212.8522	$212.85	$212.85	$212.90
Purchase #4	$215.56	3.578%	$223.2727	$223.27	$223.25	$223.30
Purchase #5	$48.65	5.527%	$51.3389	$51.34	$51.35	$51.30
Purchase #6	$129.27	3.758%	$134.128	$134.13	$134.15	$134.10
Purchase #7	$212.27	9.707%	$232.875	$232.88	$232.90	$232.90
7 purchase totals =	$1,103.64		$1,178.8227	$1,178.83	$1,178.85	$1,178.90