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	$130.64	8.706%	$142.0135	$142.01	$142.00	$142.00
Purchase #2	$107.88	12.431%	$121.2906	$121.29	$121.30	$121.30
Purchase #3	$158.54	10.248%	$174.7872	$174.79	$174.80	$174.80
Purchase #4	$238.73	10.647%	$264.1476	$264.15	$264.15	$264.10
Purchase #5	$47.97	11.247%	$53.3652	$53.37	$53.35	$53.40
Purchase #6	$100.55	10.457%	$111.0645	$111.06	$111.05	$111.10
Purchase #7	$163.51	9.406%	$178.8898	$178.89	$178.90	$178.90
7 purchase totals =	$947.82		$1,045.5584	$1,045.56	$1,045.55	$1,045.60