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	$184.86	13.233%	$209.3225	$209.32	$209.30	$209.30
Purchase #2	$157.27	12.646%	$177.1584	$177.16	$177.15	$177.20
Purchase #3	$17.48	5.805%	$18.4947	$18.49	$18.50	$18.50
Purchase #4	$159.69	4.651%	$167.1172	$167.12	$167.10	$167.10
Purchase #5	$142.57	4.446%	$148.9087	$148.91	$148.90	$148.90
Purchase #6	$187.67	4.663%	$196.4211	$196.42	$196.40	$196.40
Purchase #7	$214.77	10.323%	$236.9407	$236.94	$236.95	$236.90
7 purchase totals =	$1,064.31		$1,154.3633	$1,154.36	$1,154.30	$1,154.30