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	$9.77	12.755%	$11.0162	$11.02	$11.00	$11.00
Purchase #2	$18.65	8.815%	$20.294	$20.29	$20.30	$20.30
Purchase #3	$91.87	8.265%	$99.4631	$99.46	$99.45	$99.50
Purchase #4	$25.39	12.696%	$28.6135	$28.61	$28.60	$28.60
Purchase #5	$166.79	5.623%	$176.1686	$176.17	$176.15	$176.20
Purchase #6	$166.32	7.772%	$179.2464	$179.25	$179.25	$179.20
Purchase #7	$70.49	3.288%	$72.8077	$72.81	$72.80	$72.80
7 purchase totals =	$549.28		$587.6095	$587.61	$587.55	$587.60