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	$58.59	9.410%	$64.1033	$64.10	$64.10	$64.10
Purchase #2	$168.71	6.500%	$179.6762	$179.68	$179.70	$179.70
Purchase #3	$123.27	4.594%	$128.933	$128.93	$128.95	$128.90
Purchase #4	$242.30	7.830%	$261.2721	$261.27	$261.25	$261.30
Purchase #5	$137.94	6.758%	$147.262	$147.26	$147.25	$147.30
Purchase #6	$160.88	13.728%	$182.9656	$182.97	$182.95	$183.00
Purchase #7	$82.71	9.150%	$90.278	$90.28	$90.30	$90.30
7 purchase totals =	$974.40		$1,054.4902	$1,054.49	$1,054.50	$1,054.60