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	$224.98	9.469%	$246.2834	$246.28	$246.30	$246.30
Purchase #2	$103.79	10.214%	$114.3911	$114.39	$114.40	$114.40
Purchase #3	$58.50	4.411%	$61.0804	$61.08	$61.10	$61.10
Purchase #4	$45.39	5.309%	$47.7998	$47.80	$47.80	$47.80
Purchase #5	$37.82	7.670%	$40.7208	$40.72	$40.70	$40.70
Purchase #6	$80.27	13.280%	$90.9299	$90.93	$90.95	$90.90
Purchase #7	$131.88	7.603%	$141.9068	$141.91	$141.90	$141.90
7 purchase totals =	$682.63		$743.1122	$743.11	$743.15	$743.10