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	$184.57	4.322%	$192.5471	$192.55	$192.55	$192.50
Purchase #2	$103.27	13.412%	$117.1206	$117.12	$117.10	$117.10
Purchase #3	$216.88	12.142%	$243.2136	$243.21	$243.20	$243.20
Purchase #4	$225.93	12.138%	$253.3534	$253.35	$253.35	$253.40
Purchase #5	$237.39	7.639%	$255.5242	$255.52	$255.50	$255.50
Purchase #6	$147.97	13.622%	$168.1265	$168.13	$168.15	$168.10
Purchase #7	$164.30	6.787%	$175.451	$175.45	$175.45	$175.50
7 purchase totals =	$1,280.31		$1,405.3364	$1,405.33	$1,405.30	$1,405.30