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	$170.56	7.275%	$182.9682	$182.97	$182.95	$183.00
Purchase #2	$136.52	8.375%	$147.9536	$147.95	$147.95	$148.00
Purchase #3	$178.63	9.731%	$196.0125	$196.01	$196.00	$196.00
Purchase #4	$147.35	3.534%	$152.5573	$152.56	$152.55	$152.60
Purchase #5	$241.76	7.355%	$259.5414	$259.54	$259.55	$259.50
Purchase #6	$62.66	5.668%	$66.2116	$66.21	$66.20	$66.20
Purchase #7	$85.67	4.282%	$89.3384	$89.34	$89.35	$89.30
7 purchase totals =	$1,023.15		$1,094.5830	$1,094.58	$1,094.55	$1,094.60