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	$112.48	5.254%	$118.3897	$118.39	$118.40	$118.40
Purchase #2	$240.48	6.373%	$255.8058	$255.81	$255.80	$255.80
Purchase #3	$52.46	6.556%	$55.8993	$55.90	$55.90	$55.90
Purchase #4	$60.25	4.314%	$62.8492	$62.85	$62.85	$62.80
Purchase #5	$200.74	9.390%	$219.5895	$219.59	$219.60	$219.60
Purchase #6	$227.90	13.740%	$259.2135	$259.21	$259.20	$259.20
Purchase #7	$45.45	7.819%	$49.0037	$49.00	$49.00	$49.00
7 purchase totals =	$939.76		$1,020.7507	$1,020.75	$1,020.75	$1,020.70