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	$248.64	3.651%	$257.7178	$257.72	$257.70	$257.70
Purchase #2	$96.93	13.529%	$110.0437	$110.04	$110.05	$110.00
Purchase #3	$102.94	12.744%	$116.0587	$116.06	$116.05	$116.10
Purchase #4	$117.65	8.236%	$127.3397	$127.34	$127.35	$127.30
Purchase #5	$150.81	9.443%	$165.051	$165.05	$165.05	$165.10
Purchase #6	$101.56	10.103%	$111.8206	$111.82	$111.80	$111.80
Purchase #7	$231.72	11.310%	$257.9275	$257.93	$257.95	$257.90
7 purchase totals =	$1,050.25		$1,145.9590	$1,145.96	$1,145.95	$1,145.90