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	$194.77	8.821%	$211.9507	$211.95	$211.95	$212.00
Purchase #2	$53.44	5.709%	$56.4909	$56.49	$56.50	$56.50
Purchase #3	$86.30	11.737%	$96.429	$96.43	$96.45	$96.40
Purchase #4	$163.42	11.242%	$181.7917	$181.79	$181.80	$181.80
Purchase #5	$120.71	10.817%	$133.7672	$133.77	$133.75	$133.80
Purchase #6	$217.89	12.284%	$244.6556	$244.66	$244.65	$244.70
Purchase #7	$70.89	11.189%	$78.8219	$78.82	$78.80	$78.80
7 purchase totals =	$907.42		$1,003.9070	$1,003.91	$1,003.90	$1,004.00