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	$48.71	10.738%	$53.9405	$53.94	$53.95	$53.90
Purchase #2	$209.75	8.431%	$227.434	$227.43	$227.45	$227.40
Purchase #3	$10.85	3.816%	$11.264	$11.26	$11.25	$11.30
Purchase #4	$141.91	8.567%	$154.0674	$154.07	$154.05	$154.10
Purchase #5	$91.28	6.352%	$97.0781	$97.08	$97.10	$97.10
Purchase #6	$174.29	9.166%	$190.2654	$190.27	$190.25	$190.30
Purchase #7	$99.72	5.737%	$105.4409	$105.44	$105.45	$105.40
7 purchase totals =	$776.51		$839.4903	$839.49	$839.50	$839.50