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	$108.57	5.123%	$114.132	$114.13	$114.15	$114.10
Purchase #2	$136.69	11.526%	$152.4449	$152.44	$152.45	$152.40
Purchase #3	$152.32	5.402%	$160.5483	$160.55	$160.55	$160.50
Purchase #4	$32.59	5.384%	$34.3446	$34.34	$34.35	$34.30
Purchase #5	$50.37	8.304%	$54.5527	$54.55	$54.55	$54.60
Purchase #6	$199.62	12.384%	$224.3409	$224.34	$224.35	$224.30
Purchase #7	$99.40	3.794%	$103.1712	$103.17	$103.15	$103.20
7 purchase totals =	$779.56		$843.5346	$843.52	$843.55	$843.40