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	$50.63	7.558%	$54.4566	$54.46	$54.45	$54.50
Purchase #2	$151.46	7.528%	$162.8619	$162.86	$162.85	$162.90
Purchase #3	$155.56	11.228%	$173.0263	$173.03	$173.05	$173.00
Purchase #4	$5.41	7.269%	$5.8033	$5.80	$5.80	$5.80
Purchase #5	$160.75	9.668%	$176.2913	$176.29	$176.30	$176.30
Purchase #6	$98.28	7.808%	$105.9537	$105.95	$105.95	$106.00
Purchase #7	$115.96	6.196%	$123.1449	$123.14	$123.15	$123.10
7 purchase totals =	$738.05		$801.5380	$801.53	$801.55	$801.60