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	$107.84	9.822%	$118.432	$118.43	$118.45	$118.40
Purchase #2	$148.71	7.817%	$160.3347	$160.33	$160.35	$160.30
Purchase #3	$62.83	6.425%	$66.8668	$66.87	$66.85	$66.90
Purchase #4	$147.76	11.708%	$165.0597	$165.06	$165.05	$165.10
Purchase #5	$115.29	6.771%	$123.0963	$123.10	$123.10	$123.10
Purchase #6	$126.67	7.554%	$136.2387	$136.24	$136.25	$136.20
Purchase #7	$246.59	11.850%	$275.8109	$275.81	$275.80	$275.80
7 purchase totals =	$955.69		$1,045.8391	$1,045.84	$1,045.85	$1,045.80