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	$96.41	9.431%	$105.5024	$105.50	$105.50	$105.50
Purchase #2	$166.72	11.529%	$185.9411	$185.94	$185.95	$185.90
Purchase #3	$218.35	9.794%	$239.7352	$239.74	$239.75	$239.70
Purchase #4	$244.27	13.369%	$276.9265	$276.93	$276.95	$276.90
Purchase #5	$97.59	6.483%	$103.9168	$103.92	$103.90	$103.90
Purchase #6	$188.59	6.112%	$200.1166	$200.12	$200.10	$200.10
Purchase #7	$167.84	5.203%	$176.5727	$176.57	$176.55	$176.60
7 purchase totals =	$1,179.77		$1,288.7113	$1,288.72	$1,288.70	$1,288.60