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	$176.67	7.857%	$190.551	$190.55	$190.55	$190.60
Purchase #2	$190.89	3.734%	$198.0178	$198.02	$198.00	$198.00
Purchase #3	$218.81	11.263%	$243.4546	$243.45	$243.45	$243.50
Purchase #4	$193.70	13.221%	$219.3091	$219.31	$219.30	$219.30
Purchase #5	$62.45	6.156%	$66.2944	$66.29	$66.30	$66.30
Purchase #6	$71.68	13.106%	$81.0744	$81.07	$81.05	$81.10
Purchase #7	$78.74	3.662%	$81.6235	$81.62	$81.60	$81.60
7 purchase totals =	$992.94		$1,080.3248	$1,080.31	$1,080.25	$1,080.40