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	$203.80	12.799%	$229.8844	$229.88	$229.90	$229.90
Purchase #2	$37.70	10.194%	$41.5431	$41.54	$41.55	$41.50
Purchase #3	$216.77	3.478%	$224.3093	$224.31	$224.30	$224.30
Purchase #4	$38.36	11.522%	$42.7798	$42.78	$42.80	$42.80
Purchase #5	$107.91	5.785%	$114.1526	$114.15	$114.15	$114.20
Purchase #6	$179.54	4.387%	$187.4164	$187.42	$187.40	$187.40
Purchase #7	$243.86	11.478%	$271.8503	$271.85	$271.85	$271.90
7 purchase totals =	$1,027.94		$1,111.9359	$1,111.93	$1,111.95	$1,112.00