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	$58.79	6.133%	$62.3956	$62.40	$62.40	$62.40
Purchase #2	$209.91	5.767%	$222.0155	$222.02	$222.00	$222.00
Purchase #3	$226.33	4.329%	$236.1278	$236.13	$236.15	$236.10
Purchase #4	$65.38	11.522%	$72.9131	$72.91	$72.90	$72.90
Purchase #5	$86.53	4.756%	$90.6454	$90.65	$90.65	$90.60
Purchase #6	$86.34	4.641%	$90.347	$90.35	$90.35	$90.30
Purchase #7	$60.41	3.376%	$62.4494	$62.45	$62.45	$62.40
7 purchase totals =	$793.69		$836.8938	$836.91	$836.90	$836.70