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	$243.93	6.455%	$259.6757	$259.68	$259.70	$259.70
Purchase #2	$114.91	11.229%	$127.8132	$127.81	$127.80	$127.80
Purchase #3	$116.43	5.684%	$123.0479	$123.05	$123.05	$123.00
Purchase #4	$138.44	10.104%	$152.428	$152.43	$152.45	$152.40
Purchase #5	$115.55	7.140%	$123.8003	$123.80	$123.80	$123.80
Purchase #6	$136.32	10.746%	$150.9689	$150.97	$150.95	$151.00
Purchase #7	$163.37	7.454%	$175.5476	$175.55	$175.55	$175.50
7 purchase totals =	$1,028.95		$1,113.2816	$1,113.29	$1,113.30	$1,113.20