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	$62.26	13.279%	$70.5275	$70.53	$70.55	$70.50
Purchase #2	$29.78	13.560%	$33.8182	$33.82	$33.80	$33.80
Purchase #3	$185.62	6.807%	$198.2552	$198.26	$198.25	$198.30
Purchase #4	$137.95	13.372%	$156.3967	$156.40	$156.40	$156.40
Purchase #5	$112.39	3.752%	$116.6069	$116.61	$116.60	$116.60
Purchase #6	$232.54	11.609%	$259.5356	$259.54	$259.55	$259.50
Purchase #7	$38.41	7.352%	$41.2339	$41.23	$41.25	$41.20
7 purchase totals =	$798.95		$876.3740	$876.39	$876.40	$876.30