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	$102.25	9.236%	$111.6938	$111.69	$111.70	$111.70
Purchase #2	$174.50	9.532%	$191.1333	$191.13	$191.15	$191.10
Purchase #3	$171.86	8.447%	$186.377	$186.38	$186.40	$186.40
Purchase #4	$190.61	7.196%	$204.3263	$204.33	$204.35	$204.30
Purchase #5	$108.80	3.689%	$112.8136	$112.81	$112.80	$112.80
Purchase #6	$224.59	13.252%	$254.3527	$254.35	$254.35	$254.40
Purchase #7	$85.25	13.425%	$96.6948	$96.69	$96.70	$96.70
7 purchase totals =	$1,057.86		$1,157.3915	$1,157.38	$1,157.45	$1,157.40