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	$61.52	6.686%	$65.6332	$65.63	$65.65	$65.60
Purchase #2	$26.99	10.280%	$29.7646	$29.76	$29.75	$29.80
Purchase #3	$117.84	11.414%	$131.2903	$131.29	$131.30	$131.30
Purchase #4	$182.64	7.769%	$196.8293	$196.83	$196.85	$196.80
Purchase #5	$187.52	5.710%	$198.2274	$198.23	$198.25	$198.20
Purchase #6	$89.74	9.496%	$98.2617	$98.26	$98.25	$98.30
Purchase #7	$40.45	7.825%	$43.6152	$43.62	$43.60	$43.60
7 purchase totals =	$706.70		$763.6217	$763.62	$763.65	$763.60