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	$176.27	6.333%	$187.4332	$187.43	$187.45	$187.40
Purchase #2	$230.96	5.597%	$243.8868	$243.89	$243.90	$243.90
Purchase #3	$54.72	4.412%	$57.1342	$57.13	$57.15	$57.10
Purchase #4	$127.40	7.635%	$137.127	$137.13	$137.15	$137.10
Purchase #5	$162.36	10.814%	$179.9176	$179.92	$179.90	$179.90
Purchase #6	$97.32	8.652%	$105.7401	$105.74	$105.75	$105.70
Purchase #7	$8.59	10.233%	$9.469	$9.47	$9.45	$9.50
7 purchase totals =	$857.62		$920.7079	$920.71	$920.75	$920.60