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	$155.36	9.242%	$169.7184	$169.72	$169.70	$169.70
Purchase #2	$6.71	6.466%	$7.1439	$7.14	$7.15	$7.10
Purchase #3	$232.42	11.805%	$259.8572	$259.86	$259.85	$259.90
Purchase #4	$81.46	5.427%	$85.8808	$85.88	$85.90	$85.90
Purchase #5	$207.73	4.299%	$216.6603	$216.66	$216.65	$216.70
Purchase #6	$53.82	10.496%	$59.4689	$59.47	$59.45	$59.50
Purchase #7	$53.80	5.599%	$56.8123	$56.81	$56.80	$56.80
7 purchase totals =	$791.30		$855.5418	$855.54	$855.50	$855.60