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	$200.52	13.839%	$228.27	$228.27	$228.25	$228.30
Purchase #2	$94.25	5.631%	$99.5572	$99.56	$99.55	$99.60
Purchase #3	$171.94	10.112%	$189.3266	$189.33	$189.35	$189.30
Purchase #4	$247.74	9.182%	$270.4875	$270.49	$270.50	$270.50
Purchase #5	$72.62	6.627%	$77.4325	$77.43	$77.45	$77.40
Purchase #6	$171.59	3.568%	$177.7123	$177.71	$177.70	$177.70
Purchase #7	$206.56	9.106%	$225.3694	$225.37	$225.35	$225.40
7 purchase totals =	$1,165.22		$1,268.1555	$1,268.16	$1,268.15	$1,268.20