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	$53.53	9.840%	$58.7974	$58.80	$58.80	$58.80
Purchase #2	$23.64	3.802%	$24.5388	$24.54	$24.55	$24.50
Purchase #3	$61.40	7.612%	$66.0738	$66.07	$66.05	$66.10
Purchase #4	$85.61	12.768%	$96.5407	$96.54	$96.55	$96.50
Purchase #5	$174.61	9.170%	$190.6217	$190.62	$190.60	$190.60
Purchase #6	$155.36	13.755%	$176.7298	$176.73	$176.75	$176.70
Purchase #7	$145.25	4.552%	$151.8618	$151.86	$151.85	$151.90
7 purchase totals =	$699.40		$765.1640	$765.16	$765.15	$765.10