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	$222.96	8.781%	$242.5381	$242.54	$242.55	$242.50
Purchase #2	$246.32	12.156%	$276.2627	$276.26	$276.25	$276.30
Purchase #3	$180.91	10.713%	$200.2909	$200.29	$200.30	$200.30
Purchase #4	$102.46	3.107%	$105.6434	$105.64	$105.65	$105.60
Purchase #5	$98.71	4.536%	$103.1875	$103.19	$103.20	$103.20
Purchase #6	$58.84	4.681%	$61.5943	$61.59	$61.60	$61.60
Purchase #7	$180.75	3.116%	$186.3822	$186.38	$186.40	$186.40
7 purchase totals =	$1,090.95		$1,175.8991	$1,175.89	$1,175.95	$1,175.90