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	$242.47	7.713%	$261.1717	$261.17	$261.15	$261.20
Purchase #2	$115.82	9.396%	$126.7024	$126.70	$126.70	$126.70
Purchase #3	$72.80	7.696%	$78.4027	$78.40	$78.40	$78.40
Purchase #4	$155.68	7.689%	$167.6502	$167.65	$167.65	$167.70
Purchase #5	$67.77	6.407%	$72.112	$72.11	$72.10	$72.10
Purchase #6	$114.64	5.204%	$120.6059	$120.61	$120.60	$120.60
Purchase #7	$102.70	8.817%	$111.7551	$111.76	$111.75	$111.80
7 purchase totals =	$871.88		$938.4000	$938.40	$938.35	$938.50