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	$130.72	7.512%	$140.5397	$140.54	$140.55	$140.50
Purchase #2	$12.49	12.320%	$14.0288	$14.03	$14.05	$14.00
Purchase #3	$137.71	9.216%	$150.4014	$150.40	$150.40	$150.40
Purchase #4	$174.42	12.564%	$196.3341	$196.33	$196.35	$196.30
Purchase #5	$73.80	4.415%	$77.0583	$77.06	$77.05	$77.10
Purchase #6	$6.68	13.572%	$7.5866	$7.59	$7.60	$7.60
Purchase #7	$207.81	3.742%	$215.5863	$215.59	$215.60	$215.60
7 purchase totals =	$743.63		$801.5352	$801.54	$801.60	$801.50