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	$91.75	8.751%	$99.779	$99.78	$99.80	$99.80
Purchase #2	$10.46	13.443%	$11.8661	$11.87	$11.85	$11.90
Purchase #3	$116.34	13.131%	$131.6166	$131.62	$131.60	$131.60
Purchase #4	$204.88	6.121%	$217.4207	$217.42	$217.40	$217.40
Purchase #5	$160.31	8.785%	$174.3932	$174.39	$174.40	$174.40
Purchase #6	$99.66	10.455%	$110.0795	$110.08	$110.10	$110.10
Purchase #7	$174.91	11.799%	$195.5476	$195.55	$195.55	$195.50
7 purchase totals =	$858.31		$940.7027	$940.71	$940.70	$940.70