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	$113.94	4.332%	$118.8759	$118.88	$118.90	$118.90
Purchase #2	$17.80	4.396%	$18.5825	$18.58	$18.60	$18.60
Purchase #3	$245.45	11.369%	$273.3552	$273.36	$273.35	$273.40
Purchase #4	$194.62	11.242%	$216.4992	$216.50	$216.50	$216.50
Purchase #5	$47.79	6.267%	$50.785	$50.79	$50.80	$50.80
Purchase #6	$35.33	5.482%	$37.2668	$37.27	$37.25	$37.30
Purchase #7	$105.44	6.739%	$112.5456	$112.55	$112.55	$112.50
7 purchase totals =	$760.37		$827.9102	$827.93	$827.95	$828.00