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	$218.78	11.447%	$243.8237	$243.82	$243.80	$243.80
Purchase #2	$142.89	12.541%	$160.8098	$160.81	$160.80	$160.80
Purchase #3	$218.31	5.311%	$229.9044	$229.90	$229.90	$229.90
Purchase #4	$213.57	5.332%	$224.9576	$224.96	$224.95	$225.00
Purchase #5	$154.41	8.671%	$167.7989	$167.80	$167.80	$167.80
Purchase #6	$131.73	13.784%	$149.8877	$149.89	$149.90	$149.90
Purchase #7	$18.32	7.799%	$19.7488	$19.75	$19.75	$19.70
7 purchase totals =	$1,098.01		$1,196.9309	$1,196.93	$1,196.90	$1,196.90