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	$105.88	3.250%	$109.3211	$109.32	$109.30	$109.30
Purchase #2	$78.40	8.859%	$85.3455	$85.35	$85.35	$85.30
Purchase #3	$178.27	7.229%	$191.1571	$191.16	$191.15	$191.20
Purchase #4	$12.85	11.328%	$14.3056	$14.31	$14.30	$14.30
Purchase #5	$167.66	4.251%	$174.7872	$174.79	$174.80	$174.80
Purchase #6	$157.31	9.206%	$171.792	$171.79	$171.80	$171.80
Purchase #7	$247.32	6.343%	$263.0075	$263.01	$263.00	$263.00
7 purchase totals =	$947.69		$1,009.7160	$1,009.73	$1,009.70	$1,009.70