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	$217.88	11.627%	$243.2129	$243.21	$243.20	$243.20
Purchase #2	$213.61	4.455%	$223.1263	$223.13	$223.15	$223.10
Purchase #3	$168.75	10.819%	$187.0071	$187.01	$187.00	$187.00
Purchase #4	$70.97	4.151%	$73.916	$73.92	$73.90	$73.90
Purchase #5	$194.79	9.210%	$212.7302	$212.73	$212.75	$212.70
Purchase #6	$56.92	4.609%	$59.5434	$59.54	$59.55	$59.50
Purchase #7	$103.81	10.283%	$114.4848	$114.48	$114.50	$114.50
7 purchase totals =	$1,026.73		$1,114.0207	$1,114.02	$1,114.05	$1,113.90