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	$72.69	13.260%	$82.3287	$82.33	$82.35	$82.30
Purchase #2	$114.25	3.796%	$118.5869	$118.59	$118.60	$118.60
Purchase #3	$90.81	7.179%	$97.3292	$97.33	$97.35	$97.30
Purchase #4	$85.96	4.774%	$90.0637	$90.06	$90.05	$90.10
Purchase #5	$192.46	11.679%	$214.9374	$214.94	$214.95	$214.90
Purchase #6	$229.48	4.663%	$240.1807	$240.18	$240.20	$240.20
Purchase #7	$186.96	4.810%	$195.9528	$195.95	$195.95	$196.00
7 purchase totals =	$972.61		$1,039.3794	$1,039.38	$1,039.45	$1,039.40