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	$213.46	6.739%	$227.8451	$227.85	$227.85	$227.80
Purchase #2	$71.78	9.471%	$78.5783	$78.58	$78.60	$78.60
Purchase #3	$207.74	13.205%	$235.1721	$235.17	$235.15	$235.20
Purchase #4	$204.93	3.708%	$212.5288	$212.53	$212.55	$212.50
Purchase #5	$83.71	3.705%	$86.8115	$86.81	$86.80	$86.80
Purchase #6	$189.39	3.712%	$196.4202	$196.42	$196.40	$196.40
Purchase #7	$11.72	11.835%	$13.1071	$13.11	$13.10	$13.10
7 purchase totals =	$982.73		$1,050.4631	$1,050.47	$1,050.45	$1,050.40