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	$220.85	10.320%	$243.6417	$243.64	$243.65	$243.60
Purchase #2	$101.46	3.859%	$105.3753	$105.38	$105.40	$105.40
Purchase #3	$248.52	10.183%	$273.8268	$273.83	$273.85	$273.80
Purchase #4	$179.42	5.735%	$189.7097	$189.71	$189.70	$189.70
Purchase #5	$53.45	10.803%	$59.2242	$59.22	$59.20	$59.20
Purchase #6	$169.99	7.782%	$183.2186	$183.22	$183.20	$183.20
Purchase #7	$28.59	11.281%	$31.8152	$31.82	$31.80	$31.80
7 purchase totals =	$1,002.28		$1,086.8115	$1,086.82	$1,086.80	$1,086.70