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	$223.94	13.480%	$254.1271	$254.13	$254.15	$254.10
Purchase #2	$132.54	9.527%	$145.1671	$145.17	$145.15	$145.20
Purchase #3	$215.50	3.644%	$223.3528	$223.35	$223.35	$223.40
Purchase #4	$249.33	4.688%	$261.0186	$261.02	$261.00	$261.00
Purchase #5	$181.88	3.461%	$188.1749	$188.17	$188.15	$188.20
Purchase #6	$72.96	7.305%	$78.2897	$78.29	$78.30	$78.30
Purchase #7	$83.71	3.438%	$86.5879	$86.59	$86.60	$86.60
7 purchase totals =	$1,159.86		$1,236.7181	$1,236.72	$1,236.70	$1,236.80