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	$35.88	12.424%	$40.3377	$40.34	$40.35	$40.30
Purchase #2	$141.95	10.111%	$156.3026	$156.30	$156.30	$156.30
Purchase #3	$244.68	4.308%	$255.2208	$255.22	$255.20	$255.20
Purchase #4	$22.83	11.860%	$25.5376	$25.54	$25.55	$25.50
Purchase #5	$166.84	12.654%	$187.9519	$187.95	$187.95	$188.00
Purchase #6	$162.89	6.859%	$174.0626	$174.06	$174.05	$174.10
Purchase #7	$159.71	9.620%	$175.0741	$175.07	$175.05	$175.10
7 purchase totals =	$934.78		$1,014.4873	$1,014.48	$1,014.45	$1,014.50