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	$136.33	6.756%	$145.5405	$145.54	$145.55	$145.50
Purchase #2	$162.76	10.134%	$179.2541	$179.25	$179.25	$179.30
Purchase #3	$195.70	13.463%	$222.0471	$222.05	$222.05	$222.00
Purchase #4	$81.64	10.520%	$90.2285	$90.23	$90.25	$90.20
Purchase #5	$160.57	3.184%	$165.6825	$165.68	$165.70	$165.70
Purchase #6	$228.47	13.641%	$259.6356	$259.64	$259.65	$259.60
Purchase #7	$89.58	3.770%	$92.9572	$92.96	$92.95	$93.00
7 purchase totals =	$1,055.05		$1,155.3455	$1,155.35	$1,155.40	$1,155.30