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	$178.59	8.813%	$194.3291	$194.33	$194.35	$194.30
Purchase #2	$65.92	9.713%	$72.3228	$72.32	$72.30	$72.30
Purchase #3	$17.44	9.619%	$19.1176	$19.12	$19.10	$19.10
Purchase #4	$112.48	13.344%	$127.4893	$127.49	$127.50	$127.50
Purchase #5	$117.51	5.104%	$123.5077	$123.51	$123.50	$123.50
Purchase #6	$147.59	9.299%	$161.3144	$161.31	$161.30	$161.30
Purchase #7	$232.25	7.177%	$248.9186	$248.92	$248.90	$248.90
7 purchase totals =	$871.78		$946.9995	$947.00	$946.95	$946.90