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	$136.80	12.738%	$154.2256	$154.23	$154.25	$154.20
Purchase #2	$69.80	3.525%	$72.2605	$72.26	$72.25	$72.30
Purchase #3	$145.71	6.294%	$154.881	$154.88	$154.90	$154.90
Purchase #4	$159.58	3.682%	$165.4557	$165.46	$165.45	$165.50
Purchase #5	$83.75	11.242%	$93.1652	$93.17	$93.15	$93.20
Purchase #6	$249.30	11.659%	$278.3659	$278.37	$278.35	$278.40
Purchase #7	$117.86	7.871%	$127.1368	$127.14	$127.15	$127.10
7 purchase totals =	$962.80		$1,045.4907	$1,045.51	$1,045.50	$1,045.60