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	$167.80	10.243%	$184.9878	$184.99	$185.00	$185.00
Purchase #2	$156.84	11.519%	$174.9064	$174.91	$174.90	$174.90
Purchase #3	$86.71	12.725%	$97.7438	$97.74	$97.75	$97.70
Purchase #4	$107.41	3.420%	$111.0834	$111.08	$111.10	$111.10
Purchase #5	$154.33	8.342%	$167.2042	$167.20	$167.20	$167.20
Purchase #6	$151.40	7.359%	$162.5415	$162.54	$162.55	$162.50
Purchase #7	$93.78	11.406%	$104.4765	$104.48	$104.50	$104.50
7 purchase totals =	$918.27		$1,002.9436	$1,002.94	$1,003.00	$1,002.90