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	$78.64	6.779%	$83.971	$83.97	$83.95	$84.00
Purchase #2	$190.47	3.397%	$196.9403	$196.94	$196.95	$196.90
Purchase #3	$153.58	5.565%	$162.1267	$162.13	$162.15	$162.10
Purchase #4	$152.81	9.772%	$167.7426	$167.74	$167.75	$167.70
Purchase #5	$43.82	5.347%	$46.1631	$46.16	$46.15	$46.20
Purchase #6	$176.47	8.685%	$191.7964	$191.80	$191.80	$191.80
Purchase #7	$160.76	5.676%	$169.8847	$169.88	$169.90	$169.90
7 purchase totals =	$956.55		$1,018.6248	$1,018.62	$1,018.65	$1,018.60