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	$182.90	7.632%	$196.8589	$196.86	$196.85	$196.90
Purchase #2	$148.57	4.268%	$154.911	$154.91	$154.90	$154.90
Purchase #3	$88.86	11.652%	$99.214	$99.21	$99.20	$99.20
Purchase #4	$171.72	12.444%	$193.0888	$193.09	$193.10	$193.10
Purchase #5	$198.82	11.329%	$221.3443	$221.34	$221.35	$221.30
Purchase #6	$21.58	11.801%	$24.1267	$24.13	$24.15	$24.10
Purchase #7	$103.31	3.784%	$107.2193	$107.22	$107.20	$107.20
7 purchase totals =	$915.76		$996.7630	$996.76	$996.75	$996.70